MEMCAL    SCHOOL 


U.C.   Training  School 
for  Nurses. 


ti>v 


U*.^.^  Ua*^   ^^^. 


CHEMISTRY  FOR  NURSES 


THE  MACMILLAN  COMPANY 

NEW  YORK  •    BOSTON  •    CHICAGO  -   DALLAS 
ATLANTA  -   SAN   FRANCISCO 

MACMILLAN  &  CO.,  Limited 

LONDON  •  BOMBAY  •  CALCUTTA 
MELBOURNE 

THE  MACMILLAN  CO.  OF  CANADA,  Ltd. 

TORONTO 


CHEMISTRY  FOE  NURSES 


BY 


LC 


REUBEN   OTTENBERG,  A.M.,  M.D. 

LECTURER    TO    THE    NURSES'    TRAINING    SCHOOL,     MT.    SINAI 
HOSPITAL  ;     INSTRUCTOR    IN    BACTERIOLOGY,    COLLEGE 
OF   PHYSICIANS   AND    SURGEONS,    COLUMBIA    UNI- 
VERSITY ;    AND    ASSISTANT    IN    CLINIQAL 
MICROSCOPY,  MT.  SINAI  HOSPITAL 


If  I     60 

Cioiessio¥\ 

^SG 

THE  MACMILLAN   COMPANY 
1921 

AU  rights  reserved 


Copyright,  1914, 
By  the  MACMILLAN  COMPANY, 

Set  up  and  electrotyped.     Published  September,  igi^^ 


NoriDootr  i^ress 

J.  6.  Gushing  Co.  —  Berwick  &  Smith  Co. 

Norwood,  Mass.,  U.S.A. 


Til 


PEEFACE 

The  teaching  of  chemistry  to  nurses  is  a  new 
thing,  but  the  development  of  medicine  has  made 
it  inevitable.  Some  knowledge  of  the  fundamental 
conceptions  of  chemistry  is  as  indispensable  as 
anatomy  in  the  modern  treatment  of  disease.  In- 
deed it  puzzles  one  to  understand  how,  in  the  past, 
without  chemical  instruction,  nurses  have  made 
any  sense  at  all  of  much  that  was  taught  them  in 
materia  medica,  physiology,  and  diet  cooking. 
How  rapidly  this  opinion  is  gaining  adherents  is 
shown  by  the  responses  to  an  inquiry  sent  by  the 
author  to  the  examining  boards  of  thirty-two 
states  of  the  Union ;  in  twenty-two  states,  the 
answers  showed,  questions  in  chemistry  formed 
part  of  the  examination  for  registered  nurses. 

This  book  has  been  written  therefore  in  response 
to  what  the  author  believes  to  be  a  real  need. 
There  is  no  simple  yet  modern  textbook  on  this 
subject.  In  the  past  nurses  anxious  for  informa- 
tion were  compelled  to  refer  either  to  textbooks 
written  for  medical  students  and  much  too  difficult 
for  the   average   nurse,   or   to   school   textbooks, 

im'd 


VI  PREFACE 

written  from  a  different  point  of  view  and  paying 
no  attention  at  all  to  many  subjects  of  peculiar 
importance  to  nurses. 

Chemistry  to  the  nurse  is  an  accessory  study,  — 
an  aid  to  the  understanding  of  other  studies  of 
undoubtedly  greater  practical  importance.  For  this 
reason  the  present  book  is  to  be  used  by  the  nurse 
not  as  a  catalogue  of  facts  to  be  learned  outright, 
but  as  a  reasoned  explanation  of  things  which 
otherwise  would  remain  obscure.  The  author 
therefore  has  avoided  all  technicalities  and  has 
attempted  to  make  the  text  as  readable  and  enter- 
taining as  possible.  The  subject  of  chemistry 
with  its  innumerable  and  important  bearings  on 
everyday  life  usually  fascinates  every  beginner  who 
overcomes  the  initial  fear  of  its  technical  difficulty. 

This  book  is  the  development  of  a  short  course 
of  lectures  given  to  the  undergraduate  nurses  of 
the  Mount  Sinai  Hospital  at  various  times  in  the 
past  two  years.  The  experiments  described  have 
all  been  demonstrated  to  classes  of  nurses  and  can 
easily  be  performed  with  the  simplest  equipment. 
It  is  suggested  that  teachers  perform  these  experi- 
ments before  their  classes. 

The  author  wishes  to  thank  several  of  his  friends 
for  their  kindly  criticism:    Dr.  Samuel  Bookman, 


PREFACE  VU 

Chemist  to  Mount  Sinai  Hospital;  Miss  George, 
Dietitian  to  Mount  Sinai  Hospital ;  Dr.  A.  S.  Blum- 
garten,  author  of  "Materia  Medica  for  Nurses'*; 
and  particularly  Mr.  Joseph  Loew  of  the  De  Witt 
Clinton  High  School,  New  York. 


TABLE  OF   CONTENTS 


OnAPTEB  PAOB 

I.    Elements  and  Compounds 1 

11.    Atoms  and  Molecules 12 

in.     Chemical    Names    and    Formulas.      Chemical 

Afflnity 18 

rv.    Energy  and  Oxidation 27 

V.    Acids 36 

VI.    Bases 44 

VII.    Salts 50 

VIII.    Organic  Chemistry  .        .        .        .        .        .        .56 

IX.     Carbohydrates 65 

X.    Fats     . 79 

XI.    Proteids 90 

XII.     Digestion 101 

XIII.  Urine 113 

XIV.  Stomach  Contents  and  Feces       ....  130 

INDEX 135 


CHEMISTRY  FOR  NURSES 

CHAPTER  I 
Elements  and  Compounds 

Two  Kinds  of  Changes  in  Matter.  —  Since  the 
earliest  times  men  have  been  studying  the  different 
kinds  of  matter  or  substances  of  which  the  world  is 
composed,  and  have  noticed  that  these  substances 
frequently  undergo  changes  in  appearance  and  form. 
Gradually  they  have  come  to  see  that  these  changes 
are  of  two  different  kinds :  the  one  kind  is  more  or 
less  transient.  Thus  the  change  from  solid  to  liquid, 
as  in  the  melting  of  ice,  or  from  liquid  to  gas,  as  in 
the  boiling  of  water,  the  glowing  of  metal  when  it 
is  heated,  are  temporary  changes.  The  water  can 
freeze  again,  the  steam  can  condense,  the  metal  can 
cool.  Changes  of  this  kind  in  matter  are  known  as 
physical  changes,  and  their  study  constitutes  the 
science  of  physics. 

Chemical  Changes.  —  But  substances  also  undergo 
another  kind  of  change  much  more  permanent  in 


2  CHEMISTRY   FOR  NURSES 

nature.  Wood  may  burn  in  the  flame  until  nothing 
is  left  but  ashes,  or  metals  rust  and  lose  their  origi- 
nal appearance  entirely.  Such  deep-going  changes 
in  matter  are  known  as  chemical  changes,  and  their 
study  is  the  science  of  chemistry. 

Elements.  —  Chemical  changes  often  result  in 
breaking  up  one  substance  into  several  products. 
Thus,  for  instance,  when  a  piece  of  wood  burns  there 
are  fumes  given  off ;  at  a  certain  stage  there  is  a  black 
residue  composed  of  carbon  (charcoal) ;  and  if  the 
burning  is  continued  for  a  long  while,  white  ashes. 
The  products  of  such  chemical  changes  can  often 
be  further  decomposed  into  still  other  substances.^ 
When  this  process  is  continued,  certain  forms  of 
matter  are  finally  obtained  which  cannot  by  any 
means  whatever  be  resolved  into  other  substances. 
These  are  called  elementary  substances  or  chemical 
elements. 

Compounds.  —  By  studying  all  sorts  of  substances 
in  this  way  the  chemists  have  discovered  that  all 
the  matter  in  the  universe  is  composed  of  about 

*  When  the  combined  weights  of  all  the  substances  produced 
by  such  decompositions  are  compared  with  the  weight  of  the 
original  substance,  they  are  found  to  be  exactly  equal.  Matter 
has  been  changed  into  different  states,  but  no  matter  has  been 
made  or  destroyed.  This  is  the  law  of  the  indestructibility  of 
matter. 


ELEMENTS   AND   COMPOUNDS  3 

eighty  of  these  elements ;  everything  from  a  microbe 
to  a  star  is  composed  of  these  same  eighty  elements 
in  different  forms  and  combinations. 

It  took  centuries  to  find  this  out  because  it  is  not 
easy  to  discover  what  elements  are  present  in  a  sub- 
stance. The  reason  for  this  difl[iculty  is  that  when 
different  elements  combine  to  form  a  new  substance 
they  lose  their  properties  entirely.  The  properties 
of  the  compound  are  nothing  like  the  properties  of  the 
elements  themselves.  Who  would  think  from  the 
properties  of  water,  for  instance,  that  it  was  composed 
of  two  light  gases  which  explode  when  they  are  mixed 
together  and  ignited?  Or,  consider  common  salt, 
sodium  chloride.  It  is  a  combination  of  two  ele- 
ments, —  sodium  and  chlorine.  Chlorine  is  a  yellow 
poisonous  vapor.  Sodium  is  a  soft  metal,  very  hard 
to  keep  in  its  natural  state  because  it  corrodes  and 
combines  with  almost  everything  it  touches.  These 
two  violent  things  with  their  peculiar  properties 
combine  and  the  result  is  our  harmless  table  salt. 

Difference  between  Mixtures  and  Compounds.  — 
But  it  must  not  be  supposed  that  just  because  ele- 
ments are  mixed  together  the  result  is  necessarily 
a  new  compound.  Substances  may  be  simply 
mixed  together  very  intimately  without  undergoing 
any  combination  (in  such  a  way  as  to  form  new 


4  CHEMISTRY    FOR   NURSES 

properties)  at  all.  If  you  mix  particles  of  carbon 
(lamp  black)  and  of  sulphur,  the  mixture  has  no  new 
properties  and  the  two  kinds  of  particles  can  be 
recognized  separately  under  a  microscope.  But  if, 
instead  of  this,  sulphur  in  the  form  of  vapor  is  made 
to  pass  over  the  red-hot  charcoal,  an  entirely  new 
substance  (carbon  disulphide)  is  formed.  It  is  a 
volatile  and  strong-smelling  liquid  which  is  of  enor- 
mous importance  in  the  manufacture  of  rubber  and 
various  perfumes.  This,  then,  is  the  difference  be- 
tween a  mixture  and  a  compound :  in  a  mixture 
the  substances  are  present  in  their  original  form  and 
are  easily  separated;  in  a  compound  the  elements 
have  undergone  a  peculiar  change  by  which  they 
not  only  acquire  entirely  new  properties,  but  are 
firmly  united  so  that  it  takes  some  powerful  force 
like  great  heat  or  a  strong  electric  current  or  power- 
ful chemical  action  to  separate  them. 

All  sorts  of  elements  combine  with  each  other  and 
thus  there  are  thousands  of  compounds:  the 
number  of  possible  compounds  is  almost  infinite. 

Constant  Composition  of  Compounds.  —  In  spite 
of  the  great  number  of  compounds  formed  by  the 
union  of  different  elements  each  compound  always 
has  precisely  the  same  composition,  no  matter  under 
what  conditions  you  find  it.    If  you  take  specimens 


ELEMENTS   AND   COMPOUNDS  5 

of  water  from  a  dozen  different  sources  and  separate 
the  elements  in  them,  you  will  always  find  exactly 
the  same  proportion  of  hydrogen  and  oxygen. 
You  never  find  more  oxygen  in  one  specimen 
of  water  than  in  another.  This  fact,  that  the  ele- 
ments in  any  chemical  compound  are  always  present 
in  precisely  the  same  proportions,  is  another  one 
of  the  things  that  distinguish  compounds  from 
mixtures.  It  is  obvious,  of  course,  that  in  a  mixture 
any  amount  of  the  one  or  the  other  ingredient  may 
be  present.  There  is  a  fundamental  reason  for  this 
constancy  of  composition  of  compoimds.  This 
reason  will  be  made  clear  in  the  next  chapter. 

How  can  Different  Compoimds  be  composed  of 
the  Same  Elements  ?  —  But  the  same  elements  may 
combine  in  several  different  proportions  to  form 
several  different  compounds.  For  instance,  take  an- 
other compound  r  i  hydrogen  and  oxygen,  namely, 
peroxide  of  hydrogen.  It  is  a  combination  of  exactly 
the  same  elements  as  water,  but  the  elements  are 
combined  in  a  different  ratio.  The  amount  of  oxygen 
present  in  any  given  amount  of  peroxide  of  hydrogen 
is  twice  as  large  as  in  the  same  amount  of  water.  On 
this  account  peroxide  of  hydrogen  is  entirely  different 
in  its  properties  from  water.  It  attacks  and  de- 
composes organic  things  such  as  blood  or  bacteria. 


6  CHEMISTRY   FOR   NURSES 

But  peroxide  of  hydrogen  in  its  turn  does  not  vary. 
The  proportions  of  hydrogen  and  oxygen  obtained 
from  different  specimens  of  it  are  always  the  same. 

There  are  two  general  methods  of  studying  com- 
pounds, —  analysis  and  synthesis.  Analysis  means 
decomposition  of  a  compound  into  the  elements 
which  compose  it :  synthesis  means  combining 
different  elements  to  form  new  compounds. 

The  Most  Important  Elements.  —  Below  is  a 
partial  list  of  elements.  The  list  includes  all  the 
elements  which  are  met  in  everyday  life  and  which 
play  an  important  part  in  medicine  or  nursing. 
Many  of  them,  such  as  carbon  and  sulphur  and  the 
metals,  are  already  familiar  in  their  natural  state. 
The  student  will  easily  be  able  to  think  of  compounds 
of  most  of  the  others.  A  short  description  of  most 
of  these  is  found  in  the  appendix  to  Chapter  I. 

1  —  Aluminium  11  —  Hydrogen 

2  —  Arsenic  12  —  Iodine 

3  —  Bismuth  13  —  Iron 

4  —  Boron  14  —  Lead 

5  —  Bromine  15  —  Lithium 

6  —  Calcium  16  —  Magnesium 

7  —  Carbon  17  —  Mercury 

8  —  Chlorine  18  —  Nickel 

9  —  Copper  19  —  Nitrogen 
10  —  Gold  20  —  Oxygen 


ELEMENTS   AND   COMPOUNDS 

21  —  Phosphorus  27  —  Sodium 

22  —  Platinum  28  —  Strontium 

23  —  Potassium  29  —  Sulphur 

24  —  Radium  30  —  Tin 

25  —  Silicon  31  —  Zinc 

26  —  Silver 


IMPORTANT   ELEMENTS   AND   COMPOUNDS 

1.  Aluminium  —  a  light,  white  metal,  which,  combined 

with  other  elements  in  the  form  of  clay  or  of  va- 
rious minerals,  forms  a  large  part  of  the  earth's 
crust.  Its  compound,  aluminium  acetate,  is  used 
in  surgical  dressings. 

2.  Arsenic  —  a  metal.     Its  compounds  are  exceedingly 

poisonous,  and  some  are  used  as  drugs. 

3.  Bismuth — a  heavy,  lustrous  metal  whose  compounds 

are  mostly  insoluble  (do  not  dissolve  in  water)  and 
are  used  in  medicine.  On  account  of  being  in- 
soluble, bismuth  compounds  when  given  as  medicines 
are  found  in  the  stools  again.  They  undergo  a 
chemical  change  which  gives  the  black  color  to  bis- 
muth stools. 

4.  Boron  —  mentioned  because  of  its  compounds,  horic 

acid  and  borax. 

5.  Bromine  —  a  heavy,  very  poisonous,  and  irritating 

brown  liquid,  the  compounds  of  which,  known  as 
bromides,  are  of  great  use  in  medicine. 

6.  Calcium  —  a  yellow  metal  which  when  heated  takes 

fire  and  burns.  One  of  its  compounds  (calcium 
carbonate)  forms  marble  and  limestone;  another 
(calcium   phosphate)  is  the  chief  constituent  of 


8  CHEMISTRY   FOR   NURSES 

hones.  We  could  not  live  without  calcium  and  it 
is  present  in  all  animals  and  vegetables. 

7.  Carbon  —  occurs    as    diamond,    graphite,    charcoal. 

Its  compounds  are  very  numerous  and  all  living 
things  are  composed  chiefly  of  them. 

8.  Chlorine  —  a  poisonous,  greenish  gas,  similar  in  many 

ways  to  bromine  and  iodine.  Its  compounds,  such 
as  hydrochloric  add,  sodium  chloride,  potassium 
chlorate,  are  of  great  importance  in  physiology  and 
medicine. 

9.  Copper  —  a  common  metal,  one  of  whose  compounds, 

copper  sulphate,  is  a  valuable  cauterizing  agent. 

10.  Gold  —  a   metal   which   has   very   few   compounds. 

This  is  what  makes  it  a  *'  precious  '^  metal.  It 
does  not  combine  readily  with  other  elements,  and 
therefore  does  not  corrode  or  rust,  but  remains  un- 
changed for  centuries. 

11.  Hydrogen  —  a  non-poisonous  gas,  the  lightest  sub- 

stance known,  and  one  of  the  most  abundant 
and  important  of  all  the  elements,  —  present 
in  all  living  matter.  Not  present  as  such  in  the 
air. 

12.  Iodine  —  shining  black  crystals,  which,  dissolved  in 

alcohol,  are  the  familiar  tincture  of  iodine.  Traces 
of  it  are  found  in  the  thyroid  gland,  and  it  is  im- 
portant for  health,  though  exactly  why  is  unknown. 
Some  of  its  compounds  (iodides)  are  valuable 
drugs. 

13.  Iron  —  important  not  only  as  a  metal,  but  also  in  its 

compounds,  some  of  which  are  valuable  drugs,  and 
one  of  which,  hcemoglobin,  is  the  red  coloring  matter 
of  our  blood  and  is  essential  for  respiration. 


ELEMENTS   AND    COMPOUNDS  9 

14.  Lead  —  is  a  heavy  metal ;   it  can  easily  be  fluidified 

by  heat.  Its  soluble  compounds  are  poisonous. 
Some  of  them  are  used  in  medicine  (lead  acetate). 

15.  Lithium  —  is  a  light  metal,  some  of  whose  compounds 

are  used  in  medicine. 

16.  Magnesium  —  a   silvery   white   metal   which   burns 

brilliantly  in  the  air.  (The  flash  light  of  photog- 
raphers is  powdered  magnesium.)  Some  of  its 
compounds,  such  as  magnesium  sulphate,  citrate, 
carbonate,  and  hydroxide  (milk  of  magnesia),  are 
important  drugs. 

17.  Mercury  —  a  heavy  fluid  metal  whose  compounds  are 

familiar  and  important  drugs  {calomel,  bichloride 
of  mercury). 

18.  Nickel  —  a  metal.  - 

19.  Nitrogen  —  an  inert  (not  chemically  active)  gas  which 

forms  about  |  of  the  air.  Its  compounds,  am- 
monia, nitrous  oxide  or  laughing  gas,  nitric  add, 
niter  or  saltpeter  (potassium  nitrate),  are  used  in 
medicine.  In  the  form  of  proteid  it  is  not  only 
an  essential  food,  but  is  present  in  every  living 
cell. 

20.  Oxygen  —  is  a  colorless,  odorless  gas  which  forms 

about  J  of  the  air  and  J  of  the  earth.  It  can  com- 
bine with  almost  every  other  element,  and  the  pro- 
cess of  its  combination  is  known  as  oxidation  or 
combustion.  It  is  essential  to  respiration  and  is 
present  in  every  living  cell.  Of  its  innumerable 
compounds,  water  is  the  most  important.  Oxygen 
gas  can  be  readily  recognized  by  the  fact  that  glow- 
ing substances  are  set  on  fire  or  burning  substances 
burn  much  more  brightly  when  introduced  into  it. 


10  CHEMISTRY   FOR   NURSES 

21.  Phosphorus  —  is  a  waxlike  solid  which  shines  in  the 

dark  and  readily  catches  fire.  It  is  used  in  making 
matches  and  is  very  poisonous.  Some  of  its  com- 
pounds, such  as  sodium  phosphate,  are  used  as  drugs. 
Another  of  its  compounds,  calcium  phosphate,  forms 
about  60  %  of  hone,  and  is  also  present  in  all 
fertile  soils,  —  is,  in  fact,  essential  to  the  growth  of 
plants.  Other  important  compounds  are  present  in 
the  blood,  in  the  brain,  and  in  the  urine. 

22.  Platinum  —  a  metal  used  in  jewelry ;  does  not  enter 

into  the  body.  It  is  a  "  precious  "  metal  for  the 
same  reason  as  gold. 

23.  Potassium  —  a  shining  white  metal  which  readily 

forms  compounds  with  a  great  many  other  ele- 
ments. When  thrown  into  water  it  unites  with  it 
so  actively  as  to  take  fire.  It  has  a  great  number 
of  important  compounds,  such  as  caustic  potash 
(potassium  hydrate),  potassium  chlorate,  potassium 
iodide,  potassium  bromide,  potassium  nitrate,  and 
many  others. 

24.  Radium  —  a  peculiar  metal  which  gives  off  very  pene- 

trating rays  like  X  rays.  It  was  recently  discovered 
by  Mme.  Curie.  It  is  used  in  the  treatment  of  cer- 
tain skin  diseases  and  cancers. 
26.  Silicon  —  is  not  of  much  importance  to  our  bodies, 
but  it  is,  nevertheless,  next  to  oxygen  the  most 
abundant  element.  It  forms  a  large  part  of 
rock,  sand,  clay,  and  soil.  Glassware  contains 
much  silicon,  as  do  a  great  many  other  things 
that  we  handle;  it  is  contained  in  the  many 
forms  of  stone  and  crockery  dishware.  It  is  very 
insoluble. 


ELEMENTS  AND  COMPOUNDS  11 

26.  Silver  —  a  metal,  some  of  whose  compounds  such  as 

silver  nitrate,  argyrol,  protargol,  are  used  in 
medicine. 

27.  Sodium  —  a    very   widespread   element,    the    sister 

metal  of  potassium,  and  with  very  similar  proper- 
ties. Some  of  its  compounds,  as  sodium  chloride, 
carbonate,  bicarbonate,  are  important  constituents  of 
the  blood. 

28.  Strontium  —  is    somewhat    similar    to    sodium    and 

potassium.  Some  of  its  compounds,  such  as  stron- 
tium bromide,  are  used  as  drugs. 

29.  Sulphur  —  is  a  yellow,  inflammable  solid  used  directly 

as  a  drug.  Its  compounds,  such  as  sulphuric  add, 
magnesium  sulphate,  etc.,  are  important  in  medicine. 
It  is  found  in  many  parts  of  the  body,  such  as  skin 
and  hair. 

30.  Tin  —  a  metal. 

31.  Zinc  —  a  metal  some  of  whose  insoluble  compounds, 

such  as  zinc  oxide,  are  used  in  medicine  for  their 
soothing  properties.  Its  soluble  compounds,  like 
zinc  sulphate  and  zinc  sulphocarbolate,  are  poison- 
ous and  are  used  as  disinfectants  and  cauterizing 
agents. 


CHAPTER  II 
Atoms  and  Molecules 

The  Use  of  Hypotheses  m  Science.  —  In  order 
to  explain  the  phenomena  of  nature,  scientists  often 
use  hypotheses,  or  working  theories.  These  are  sup- 
positions which  explain  the  facts,  but  which  for  the 
time  being  cannot  be  proved  completely.  One  of 
the  most  useful  and  important  of  these  hypotheses 
is  the  atomic  theory ,  —  the  idea  that  all  substances  are 
composed  of  extremely  minute  particles.  Although 
nobody  has  ever  seen  one  of  these  particles,  the 
theory  is  so  useful  and  explains  so  much  that  the 
whole  development  of  modern  chemistry  has  been 
built  up  on  it. 

Molecules.  —  Suppose  that  we  commenced  to 
divide  any  substance,  say  a  drop  of  water,  into 
smaller  and  smaller  particles,  and  suppose  that  we 
had  instruments  fine  enough  so  that  we  could  con- 
tinue this  division  as  long  as  we  wanted  to,  we  would 
finally  reach  a  particle  so  small  that  if  it  could  be 
further  divided,  it  would  no  longer  be  water.     These 

12 


ATOMS  AND   MOLECULES  13 

particles  of  which  water  is  believed  to  be  formed 
are  called  molecules. 

If  the  molecule  of  water  were  broken  up  into  its 
constituents,  hydrogen  and  oxygen,  it  would  no 
longer  have  the  properties  of  water.  Hence  a  mole- 
cule is  defined  as  the  smallest  weight  of  any  kind  of 
matter  in  which  the  original  properties  of  the  matter 
are  retained. 

Atoms.  —  But  suppose  that  instead  of  starting 
with  a  compound  we  were  to  start  with  an  element 
itself.  Here,  too,  an  overwhelming  array  of  evidence 
has  led  scientists  to  make  the  hypothesis  that  ulti- 
mately particles  would  be  reached  which  could  not 
be  further  subdivided.  These  particles  are  known 
as  atoms. ^ 

Molecviles  Composed  of  Atoms.  —  In  the  first 
chapter  it  was  stated  that  the  composition  of  any 
compound  is  absolutely  constant;  when  any  com- 
pound is  analyzed  into  its  elements  we  always  get 
exactly  the  same  amount  of  each  of  the  elements 
from  any  given  amount  of  the  compound.  We  see 
now  why  this  is  so.     Each  molecule  of  a  compound 

^  Recent  discoveries  in  connection  with  radium  and  X  rays 
have  brought  to  our  knowledge  particles  far  smaller  even  than 
atoms,  —  particles  out  of  which  probably  atoms  themselves  are 
made. 


14  CHEMISTRY  FOR  NURSES 

has  the  same  number  of  atoms  as  every  other  molecule 
of  the  compound.  Every  molecule  of  water  has 
one  atom  of  oxygen  and  two  atoms  of  hydrogen. 
Therefore,  water,  no  matter  where  or  how  obtained, 
always  has  constant  amounts  of  oxygen  and  hydro- 
gen. 

Size  of  Molecules.  —  The  absolute  size  of  atoms 
and  molecules  is  not  known.  All  atoms  and  even 
the  largest  molecules,  those  known  to  contain  thou- 
sands of  atoms,  are  far  too  small  to  be  seen  through 
the  most  powerful  microscope.  It  will  give  you  some 
idea  of  their  size  to  know  that  it  has  been  calculated 
that  if  a  single  drop  of  water  were  magnified  to  the 
size  of  the  earth,  the  molecules  would  be  something 
like  tbe  size  of  baseballs. 

Weight  of  Atoms.  —  The  atoms  of  the  different 
elements  have  different  weights ;  the  atoms  of  the 
same  elements  are  all  alike.  Though  their  absolute 
weights  are  not  known,  the  relative  weights  of  all 
the  atoms  are  known  with  great  accuracy.  Hydro- 
gen is  the  lightest  and  is  taken  as  the  standard, 
while  the  atom  of  radium,  one  of  the  heaviest,  weighs 
two  hundred  and  twenty-five  times  as  much  as  the 
atom  of  hydrogen. 


ATOMS   AND   MOLECULES  15 

PHYSICAL  STATE   OF  MATTER 

Changes  in  Physical  State  of  Molecules.  —  A  sub- 
stance remains  unchanged  no  matter  what  vicissi- 
tudes it  goes  through  as  long  as  the  atoms  in  its 
molecules  remain  together.  The  molecule  of  water 
is  the  same  whether  in  steam,  or  water,  or  ice.  But 
the  positions  and  motions  of  the  molecules  may  vary. 
In  steam  and  in  all  gases  the  molecules  are  separated 
by  space  and  vibrate  to  and  fro.  This  causes  the 
pressure  of  gas  on  the  containing  wall  (for  instance, 
the  pressure  of  the  gas  in  a  balloon).  In  fluids  the 
molecules  are  packed  much  more  closely  together, 
but  they  still  move  to  and  fro.  In  solids  their  rela- 
tive positions  are  fixed.  The  physical  state  of  a  sub- 
stance, whether  it  is  solid,  fluid,  or  gas,  depends  on 
temperature  and  pressure,  and  it  is  possible  to  ob- 
tain most  substances  in  any  one  of  these  three  forms. 

Thus  we  have  reached  a  different  idea  of  chemical 
and  physical  changes  from  that  given  in  the  first 
chapter.  Chemical  changes  are  those  in  which  the 
atoms  in  the  molecule  are  changed.  Physical  changes 
are  changes  in  which  the  molecules  retain  all  their  atoms 
intact.  This  is  the  reason  that  chemical  changes  are 
generally  more  permanent  and  deep-going  than  physi- 
cal changes. 


16  CHEMISTRY   FOR   NURSES 

Many  physical  processes,  such  as  dissolving,  boil- 
ing, distilling,  crystallizing,  are  made  use  of  in  chemi- 
cal operations. 

Solution.  —  When  sugar  or  salt  is  put  into  water 
it  disappears  (dissolves),  but  its  presence  in  the  water 
can  be  recognized  by  the  taste.  If  more  salt  or 
sugar  is  gradually  added,  a  limit  is  finally  reached, 
at  which  no  more  can  be  dissolved.  The  solution  is 
saturated}  If  now  the  water  is  warmed,  it  will  dis- 
solve some  more  sugar  or  salt,  for  the  solubility  of 
most  solid  substances  increases  as  the  temperature 
rises.  If  the  solution  is  saturated  while  very  hot 
and  then  allowed  very  slowly  to  cool,  some  of  the 
sugar  or  salt  will  appear  again  in  the  form  of  crystals. 

Crystallization.  —  Likewise,  if  some  of  the  water 
evaporates  from  a  saturated  solution,  crystals  form. 
Crystallization  is  one  of  the  methods  used  in  chemis- 
try and  in  manufacturing  to  obtain  substances  in  a 
pm*e  state.  For  a  crystal  contains  not  a  mixture  of 
two  substances,  but  only  one  substance. 

The  Right  Solvent  must  be  Chosen.  —  Substances 
may  dissolve  not  only  in  water,  but  in  other  fluids. 
Moreover,  the  solubility  of  different  substances  in 
different  fluids  varies  greatly.    Thus  water  will  dis- 

^  See  Chapter  on  Solutions  in  Blumgarten's  "  Materia  Medica 
for  Nurses." 


ATOMS   AND   MOLECULES  17 

solve  large  amounts  of  salt,  but  will  not  dissolve  fat 
at  all.  Ether,  on  the  other  hand,  dissolves  fat  readily, 
but  not  salt. 

Solubility  of  Gases.  —  A  fluid  may  dissolve  not 
only  solids,  but  also  various  fluids  and  gases.  For 
instance,  ether  or  chloroform  will  dissolve  to  some 
extent  in  water.  A  familiar  example  of  a  dissolved 
gas  is  carbonated  water  (carbonic  acid  gas  dissolved 
in  water).  Oxygen  is  soluble  in  water  and  fish  live 
by  breathing  dissolved  oxygen  gas.  Dissolved  gases 
do  not  follow  the  same  rule  with  regard  to  tempera- 
ture as  dissolved  solids,  but  on  the  contrary  as  the 
temperature  rises,  less,  not  more,  of  the  gas  will 
dissolve.^ 

Distillation.  —  When  fluids  change  to  gases  at 
ordinary  temperature  we  speak  of  the  process  as 
evaporation.  When  heat  is  applied  so  that  the 
change  from  fluid  to  gas  is  violent  we  call  it  boiling. 
When  gases  are  cooled  sufficiently,  or  are  subjected 
to  pressure,  or  both,  they  condense  and  form  liquids 
again.  Distilling  consists  of  first  boiling  a  fluid 
and  then  cooling  the  escaping  vapor  to  a  liquid. 
Distillation  is  very  useful  in  purifying  and  separating 
various  substances. 

1  The  reason  that  boiled  water  tastes  "  flat "  is  that  the  heat 
drives  all  the  dissolved  air  out  of  it. 
c 


CHAPTER  III 

Chemical    Names    and    Formulas.      Chemical 
Affinity 

Chemical  Names  tell  the  Composition  of  Sub- 
stances. —  To  make  the  study  of  their  science  as 
easy  as  possible,  the  chemists  have  tried  to  give 
every  compound  a  name  that  in  general  tells  what 
its  composition  is.  This  can  be  done,  however,  only 
with  relatively  simple  compounds.  When  we  get 
molecules  that  contain  two  or  three  hundred  atoms 
it  is  impossible  to  name  them  all,  but  in  the  more 
simple  compounds  the  name  indicates  the  atoms, 
and  even  in  the  very  complicated  ones  the  name 
often  tells  a  great  part  of  the  story. 

Thus,  combinations  of  oxygen  are  known  as 
oxides.  Some  of  the  simple  oxides  already  familiar 
to  you  are  carbon  dioxide  (the  bubbles  of  carbonated 
beverages),  nitrous  oxide  (laughing  gas),  zinc  oxide. 
Most  of  the  elements  can  form  oxides. 

Many  (but  not  all)  compounds  of  chlorine  are 
called  chlorides.  It  is  evident  from  the  name  that 
sodium  chloride  is  a  compound  in  which  two  ele- 
ments, sodium  and  chlorine,  have  combined.    The 

18 


CHEMICAL   NAMES   AND    FORMULAS  19 

same  is  true  of  bromides  and  iodides  and  sulphides. 
Each  of  them  is  a  simple  combination  of  some  ele- 
ment with  bromine  or  iodine  or  sulphur.  In  general, 
the  name  suggests  the  combination. 

Reason  for  Using  Formulas.  —  In  the  more  com- 
plicated parts  of  chemistry  short  names  have  to  be 
used  for  long  compounds.  But  in  order  to  state 
simply  and  completely  what  atoms  form  each  mole- 
cule a  system  of  abbreviations  has  been  invented. 
In  addition  to  the  name  for  each  compound  there  is 
a  formula  that  tells  in  a  few  letters  the  chemical 
structure.  In  writing  formulas  each  element  has  a 
letter  or  pair  of  letters  which  represents  it.  These 
abbreviations  are  used  by  all  chemists  of  the  world ; 
a  chemist  speaks  a  sort  of  international  language. 
It  helps  greatly  in  understanding  chemistry  to  know 
the  most  important  of  these  abbreviations :  — 


Bromine  . 

.   Br. 

Iron      .     .     . 

Fe. 

(for  the  Latin 

Calcium   . 

.  Ca. 

Iodine       .     . 

I. 

ferrum) 

Carbon    . 

.  C. 

Oxygen      .     . 

,    0. 

Chlorine  . 

.  CI. 

Nitrogen   .     . 

.    N. 

Hydrogen 

.   H. 

Phosphorus    . 
Potassium 

.    P. 
K. 

Because  phosphorus  was  known  before  potassium 
it  has  the  initial  letter  '^  P  "  for  its  abbreviation; 
potassium  must  have  some  other  initial  and  so  the 


20  CHEMISTRY   FOR  NURSES 

Latin  name  of  kalium  is  used  for  potassium  and  its 
abbreviation  is  simply  K. 

Sodium   .     .     .    Na.        (natrium) 

Silver       .     .     .    Ag.         (argentum,  Latin  for  silver) 

Sulphur   .     .     .    S. 

How  to  interpret  Formulas   of    Compounds.  — 

Each  initial  written  alone  stands  for  a  single  atom. 
When  two  or  more  initials  are  written  together  they 
stand  for  a  compound  whose  molecule  contains  as 
many  of  each  kind  of  atom  as  is  represented  by  the 
little  figure  written  to  the  right  of  the  letter.  For 
example:  KI  means  a  molecule  containing  one 
atom  of  potassium  and  one  of  iodine  (potassium 
iodide).  The  abbreviation  CO2  means  that  each 
molecule  of  carbon  dioxide  contains  two  atoms  of 
oxygen  and  one  of  carbon.  The  formula  for  silver 
nitrate  is  AgNOs,  which  means  that  one  atom  of 
silver  is  united  with  one  of  nitrogen  and  three  of 
oxygen.  Thus  there  are  five  atoms  in  the  one 
molecule  of  silver  nitrate.  The  formula  tells  at 
once  exactly  what  silver  nitrate  is. 

CHEMICAL  AFFINITY 

What  makes  Atoms  Unite  ?  —  Why  do  the  atoms 
unite  to  form  molecules?    In  order  to  explain  this 


CHEMICAL  NAMES   AND   FORMULAS  21 

scientists  have  had  to  assume  the  existence  of  a 
powerful  and  little  understood  force  known  as 
chemical  affinity.  This  tendency  to  unite  with 
other  atoms  is  very  strong  in  some  instances,  very 
weak  in  others.  Thus  the  tendency  of  the  elements 
sodium  and  potassium  to  combine  with  other  ele- 
ments is  so  great  that  it  is  extremely  hard  to  keep 
these  substances,  even  when  one  gets  them,  in  a  pure 
state.  They  combine  with  anything  they  touch. 
When  thrown  into  water  potassium  combines  with 
it  so  violently  as  to  burst  into  flames.  On  the 
other  hand  some  elements,  such  as  gold  and  plati- 
num, have  very  Httle  tendency  to  unite  with  other 
elements  and  they  form  only  a  few  compounds  and 
these  with  difficulty.  This  is  why  they  are  used  as 
jewelry. 

Special  Affinities  of  Different  Atoms.  —  Not  only 
do  the  atoms'  vary  in  the  strength  of  their  imions, 
but  they  show  peculiar  preferences;  each  atom 
shows  a  greater  tendency  to  imite  with  certain 
atoms  than  with  others.  The  laws  that  govern  this 
chemical  affinity  are  quite  definite,  so  that  when  a 
number  of  different  lands  of  atoms  are  mixed  together 
in  such  a  way  as  to  be  free  to  combine,  one  can  always 
predict  with  certainty  which  ones  will  unite  with 
each  other. 


22  CHEMISTRY   FOR  NURSES 

Thus  if  any  metal  such  as  iron,  or  even  silver  or 
gold,  is  put  into  a  watery  solution  of  the  element 
chlorine,  the  metal  will  always  unite  with  the 
chlorine,  —  never  with  oxygen  or  hydrogen,  because 
the  chemical  affinity  of  chlorine  for  all  metals  is  very 
great.  On  the  other  hand,  most  metals,  if  kept  in 
water  containing  no  chlorine,  or  even  in  moist  air,  will 
gradually  rust  or  tarnish,  due  to  union  with  oxygen. 

THE  USE   OF  CHEMICAL  FORMULAS 

To  show  how  we  can  express  chemical  reactions 
or  changes  and  think  out  how  they  will  happen,  let 
us  take  the  action  of  hydrochloric  acid  on  silver 
nitrate.  Hydrochloric  acid  contains  to  each  mole- 
cule one  atom  of  hydrogen  and  one  of  chlorine.  Its 
formula  is  HCl. 

Mix  a  drop  of  clear  silver  nitrate  solution  in  a 
test  tube  with  a  little  hydrochloric  acid ;  a  thick, 
white  substance  or  precipitate  forms  at  once.^  Silver 
has  a  very  powerful  affinity  for  chlorine  and  when 
they  unite  they  form  silver  chloride.  This  is  what 
the  precipitate  is  composed  of. 

^A  precipitate  is  a  solid  formed  in  a  solution  as  a  "result  of 
chemical  action.  The  fluid  can  be  separated  from  the  solid 
by  filtering  through  filter  paper.  When  this  is  done,  the  clear 
fluid  that  comes  through  the  paper  is  known  as  the  filtrate,  the 
solid  powder  left  on  the  paper  is  called  the  residue. 


CHEMICAL   NAMES   AND    FORMULAS  23 

The  formula  which  expresses  what  happens  is :  — 
AgNOs     +         HCl  =      AgCl       +      HNO, 

(Silver  Nitrate  +  Hydrochloric  Acid  =  Silver  Chloride  +  Nitric  Acid) 

This  says  that  on  adding  silver  nitrate  to  hydro- 
chloric acid  the  silver  leaves  its  combination  with 
nitrogen  and  oxygen  and  joins  the  chlorine,  for  which 
it  has  a  greater  affinity.  The  hydrogen  which  was 
originally  present  in  the  hydrochloric  acid  being 
torn  from  its  chlorine  unites  with  the  equally  deserted 
nitrogen-oxygen  combination  to  form  another  new 
substance  which  will  later  be  recognized  as  nitric 
acid.  Thus  formulas  show  the  exchange  of  atoms 
between  molecules. 

Any  compound  which  contains  chlorine  united 
with  one  other  element  will  act  in  the  same  way  as 
hydrochloric  acid  when  brought  into  contact  with  a 
silver  compound. 

Thus  let  the  student  find  out  what  happens  if 
sodium  chloride  (NaCl)  instead  of  hydrochloric  acid 
(HCl)  is  mixed  with  silver  nitrate.  Write  the 
formula. 

VALENCE 

The  reader  will  have  already  noticed  that  in 
forming  compounds  some  atoms  combine  only  with 
one  other  atom,  others  join  with  two,  three,  or  more. 
Thus  the  atom  of  oxygen  unites  with  two  atoms  of 


24  CHEMISTRY   FOR  NURSES 

hydrogen  to  form  the  molecule  of  water  (H2O), 
while  the  atom  of  chlorine  unites  with  only  one 
atom  of  hydrogen  to  form  hydrochloric  acid  (HCl). 
This  is  subject  to  a  definite  rule  which  explains  why 
the  molecule  of  any  substance  contains  always  fixed 
numbers  of  the  same  atoms  grouped  in  the  same 
way.  This  explanation  is  really  another  working 
hypothesis,  known  as  the  theory  of  valence. 

Valences  are  Imaginary  Points  of  Attachment  for 
Other  Atoms.  —  Imagine  the  atom  as  having  arms  by 
which  it  can  hold  on  to  the  arms  of  other  atoms. 
Each  kind  of  atom  has  always  a  fixed  number  of  arms, 
or  valences,  as  they  are  more  properly  called.  Thus, 
for  instance,  the  atoms  of  hydrogen,  sodium,  potas- 
sium, chlorine,  bromine,  iodine,  have  each  only 
one  arm  to  hold  on  to  the  other  atoms  with.  When 
they  unite  with  each  other  these  atoms  therefore 
form  compounds  having  two  atoms  only  to  each 
molecule.  Picture  to  yourself  the  atoms  with  their 
imaginary  arms:  — 

Hydrochloric  Acid    @ (3) 

Potassium  Iodide      @ (T) 

Sodium  Bromide       @ @ 

The  atom  of  oxygen  as  well  as  that  of  sulphur  has 
two  such  arms  or  valences.    The  atom  of  nitrogen 


CHEMICAL   NAMES   AND    FORMULAS  25 

has  three  (and  in  reality  it  has  two  extra  arms  which 
it  occasionally  can  use,  but  which  in  its  ordinary 
combinations  it  does  not  use).  The  atom  of  carbon 
has  four  arms. 

A  knowledge  of  these  facts  will  enable  you  to 
understand  much  more  clearly  the  reason  for  the 
structure  of  some  of  the  molecules  that  we  have  been 
considering.  Thus  take,  for  instance,  the  molecule  of 
water  (H2O).  In  water  we  have  the  two-armed 
atom,  oxygen,  holding  with  each  of  its  arms  to  the 
arm  of  a  one-armed  atom,  hydrogen,  thus :  — 

® — ® — ® 

Or  consider  ammonia  (NH3).  Here  we  have  the 
nitrogen  atom  holding  by  its  three  arms  to  the  arms 
of  three  atoms  of  hydrogen :  — 

Y 

Two  atoms  may  often  be  joined  by  more  than  one 
arm  or  valence.  Thus,  for  instance,  in  CO2  (carbon 
dioxide)  the  carbon  atom  divides  its  four  arms,  giving 
two  to  each  of  the  oxygen  atoms  with  which  it  is 
united :  — 


26  CHEMISTRY   FOR  NURSES 

What  is  meant  by  Structural  Formulas?  —  All 

the  complicated  structure  of  the  much  larger  mole- 
cules of  the  more  complex  compoimds  is  built  up  in 
exactly  the  same  way.  Each  atom  holds  to  the 
other  atoms  by  one  or  more  of  its  available  arms. 
Those  formulas  which  are  written  out  in  such  a  way 
as  to  show  how  each  atom  of  the  molecule  is  attached 
to  the  others  by  the  proper  number  of  valences  are 
known  as  structural  formulas,  because  they  show 
what  is  believed  to  be  the  actual  structure  of  the 
molecule.  Thus  the  structural  formula  of  silver 
nitrate^  AgNOs,  is :  — 


Write  the  structural  formula  for  potassium  ni- 
trate, KNO3  (niter,  saltpeter). 


CHAPTER  IV 
Energy  and  Oxidation 

ENERGY 

Even  superficial  observation  shows  that  there 
must  be  some  close  connection  between  chemical 
changes  and  such  manifestations  as  heat,  light, 
electricity,  and  motion.  Almost  all  combustions,  for 
instance,  raise  the  temperaturej  and  many  of  them 
produce  light  as  well.  Any  chemical  reaction  that 
occurs  suddenly  may  show  violent  motion  in  the  re- 
sulting explosion  (gunpowder,  for  instance).  And 
every  one  knows  that  the  electric  current  comes  from 
the  interaction  of  the  chemicals  that  are  put  into  an 
electric  battery. 

And,  on  the  other  hand,  not  only  do  chemical 
changes  produce  heat,  light,  or  electricity,  but  just 
as  often  heat,  light,  or  electricity  produce  chemical 
changes.  The  roasting  of  coffee,  the  bleaching  of 
muslin,  and  the  silver  plating  of  household  utensils 
by  means  of  the  electric  current  are  everyday  in- 
stances of  this. 

27 


28  CHEMISTRY   FOR  NURSES 

How  Different  Forms  of  Energy  are  Related.  — 

What  is  the  connection  between  chemical  changes 
and  all  these  forces?  Or  perhaps  before  we  try  to 
answer  that  we  should  ask :  Is  there  any  connection 
between  these  different  forces  themselves  f  There  is. 
They  are  all  of  them  different  forms  of  motion. 

The  first  inkling  of  this  remarkable  fact  came  as 
far  back  as  the  beginning  of  the  nineteenth  century, 
when  Count  Rumford  proved  that  by  continued 
friction  one  could  produce  heat  in  any  amount.^ 
Hence,  he  said,  heat  is  not  a  material  substance,  but 
a  mode  of  motion.  Gross  motion  by  friction  is  con- 
verted into  motion  of  molecules.  (Before  that  time 
heat  had  been  regarded  as  a  fluid.) 

Forms  of  Energy  mutually  Convertible.  —  And 
then  as  a  result  of  a  series  of  wonderful  discoveries 
it  gradually  became  clear  that  by  suitable  means 
any  one  of  these  forms  of  so-called  energy  could  he  con- 
verted into  any  other.  Practical  inventions  grew  out 
of  these  discoveries.  The  steam  engine  was  invented 
to  convert  heat  into  motion.  But  the  heat  that 
drives  the  steam  engine  comes  from  the  burning  of 
coal,  —  a  chemical  process.  So  the  steam  engine  is 
really  a  machine  for  converting  chemical  energy  into 
motion.  The  motion  provided  by  the  steam  engine 
^  The  heat  produced  by  friction  is  what  lights  a  match. 


ENERGY   AND    OXIDATION  29 

in  turn  can  be  changed  to  electricity  by  the  electric 
dynamo  and  sent  on  wires  to  long  distances.  And 
the  electric  current  of  the  dynamo  provides  both 
light  and  heat  or  is  converted  back  into  motion 
again  at  convenient  places  by  the  electric  motor. 

Conservation  of  Energy.  —  From  all  this  resulted 
a  great  generalization  (first  formulated  by  Mayer, 
a  German  physician,  about  1840).  It  is  known  as 
the  principle  of  the  conservation  of  energy  and  is  re- 
garded to-day  as  one  of  the  most  fundamental  doc- 
trines of  all  scientific  thought.  The  principle  in 
brief  is  that  energy  can  neither  be  created  nor  destroyed, 
neither  come  into  existence  nor  be  annihilated. 
When  energy  seems  to  have  been  produced  it  has 
really  only  been  changed  from  some  hidden  to  some 
visible  form ;  when  energy  seems  to  have  been  lost 
it  has  only  been  dissipated,  not  destroyed. 

Hidden  Energy  of  Chemical  Compoimds.  —  Now 
let  us  go  back  to  our  question.  What  connection  is 
there  between  chemical  change  and  all  these  different 
forms  of  energy?  It  is  this:  when  energy  in  any 
form  is  manifested  as  the  result  of  a  chemical  pro- 
cess, that  energy  must  have  been  lying  hidden  in  the 
substances  that  entered  into  the  chemical  process. 
When  coal  burns  the  heat  is  not  newly  created,  but 
is  energy  that  has  been  lying  dormant,  locked  up  in 


30  CHEMISTRY   FOR   NURSES 

the  molecules  of  the  coal  for  untold  ages.  And,  con- 
versely, when  energy  is  used  to  bring  about  a  chemical 
change,  that  energy  is  not  lost,  but  put  into  the  newly 
formed  chemical  substances}  And  from  these  sub- 
stances it  can  be  liberated  again  either  in  the  same 
or  another  form,  only  by  a  subsequent  chemical 
change.  The  energy  of  the  coal  was  obtained  from 
the  sun's  rays  millions  of  years  ago.  All  chemical 
processes  either  use  up  or  free  energy. 

The  Animal  Body  a  Machine  for  Transformation 
of  Energy.  —  Of  what  significance  is  all  this  to  us  ? 
We  are  interested,  first  of  all,  in  the  care  of  the  hu- 
man body. .  ^'  A  living  body  is  a  machine,  by  which 
energy  is  transformed,  in  the  same  sense  as  a  steam 
engine  is  so,  and  all  its  movements  are  to  be  accounted 
for  by  the  energy  which  is  supplied  to  it."     (Huxley.) 

Measuring  Energy.  —  J^s  we  need  standards  to 
measure  weight  and  distance,  so  also  we  need  a  stand- 
ard to  measure  so  universal  a  commodity  as  energy. 
A  number  of  such  standards  have  been  proposed  and 
used  for  special  purposes  (for  instance,  the  foot 
pound,  the  horse  power).    But  the  standard  in  most 

*  Just  so  work  done  in  lifting  a  weight  is  not  lost,  but  can  be 
recovered  again  if  the  weight  in  falling  is  connected  with  a  pulley. 
The  energy  latent  in  the  lifted  weight  might  be  compared  to 
the  energy  in  the  altered  molecule. 


ENERGY  AND   OXIDATION  31 

general  use  (and  the  one  most  important  to  us  because 
it  is  used  in  measuring  the  hidden  energy  of  foods) 
is  based  on  heat.  The  unit  is  the  amount  of  heat 
needed  to  raise  one  kilogram  of  pure  water  one  degree 
on  the  centigrade  scale,^  and  this  amount  of  heat  is 
called  a  calorie. 

The  Meaning  of  '^  Food  Value. '^  —  Thus  when  we 
say  that  a  gram  of  starch  has  four  calories,  or  a  gram 
of  fat  nine  calories,  we  mean  that  the  complete  burn- 
ing up  of  these  substances  (whether  in  the  test  tube 
or  in  the  body)  would  produce  enough  heat  to  raise, 
respectively,  four  and  nine  kilograms  of  water  one 
degree  on  the  centigrade  scale.  Or  if  we  say  that  a 
child  of  one  year  needs  every  day  seventy  calories 
for  every  kilogram  (one  thousand  grams)  of  body 
weight,  we  mean  that  the  child  needs  food  which  if 
burnt  up  would  provide  that  amount  of  energy.  So 
substances  have  "  food  value  ''  in  proportion  as  they 
supply  the  body  with  energy.  Water  and  salts  are 
absolutely  essential  in  the  diet,  but  in  this  sense  they 
have  no  '^  food  value." 

OXIDATION 

Energy  can  be  manifested  by  all  sorts  of  chem- 
ical   changes;     but    the   kind    of  chemical   change 

1  From  0°  C.  to  1°  C. 


32  CHEMISTRY   FOR  NURSES 

which  most  commonly  produces  energy  is  oxidation^ 
the  entering  of  any  substance  into  combination  with 
oxygen. 

What  happens  in  Oxidation?  —  This  was  dis- 
covered by  the  great  French  chemist  Lavoisier 
soon  after  the  discovery  of  oxygen  itself  in  1774, 
It  was  noticed  that  oxygen  was  consumed  or  trans- 
formed during  the  combustion  of  any  substance,  and 
that  the  weight  of  the  substance  (or  of  its  products) 
was  increased  by  just  so  much  as  the  weight  of  the 
oxygen  that  disappeared. 

Oxidation  may  go  on  slowly j  as  in  the  rusting  of 
iron  or  the  glowing  of  charcoal.  Or  it  may  go  on 
very  rapidly  with  the  liberation  of  heat  and  light. 
This  latter  is  called  combustion.  Substances  which 
oxidize  slowly  in  the  air  (which  contains  only  about 
20  %  of  oxygen)  will  burn  brightly  if  put  in  pure 
oxygen.  Thus  a  piece  of  glowing  charcoal  or  a 
glowing  match  will  flar«  up  with  a  brilliant  white 
light  for  a  few  moments  if  dropped  into  a  test  tube 
filled  with  oxygen  (from  an  oxygen  tank  such  as  is 
used  for  the  sick).  This  combustion  lasts  only  a 
few  moments,  until  all  the  oxygen  in  the  tube  has 
been  used  up.  Or  a  piece  of  steel  wire  (a  watch 
spring),  which  of  course  oxidizes  only  very  slowly  in 
the  air,  will  burn  with  a  brilliant  white  light  if  heated 


ENERGY   AND    OXIDATION  33 

to  redness  in  a  Bunsen  flame  ^  and  held  in  a  stream, 
of  pure  oxygen. 

Oxidation  may  decompose  Substances.  —  Oxida- 
tion may  mean  merely  the  attachment  of  oxygen 
atoms  to  other  atoms  without  any  very  extensive 
breaking  up  of  molecules ;  thus  when  a  piece  of 
phosphorus  or  a  piece  of  sulphur  burns  in  the  air, 
phosphorus  or  sulphur  atoms  unite  directly  with 
oxygen  atoms.  Or  oxidation  may  mean  the  complete 
breaking  up  of  complicated  molecules  so  that  the  vari- 
ous atoms  can  combine  with  oxygen. 

An  instance  of  the  latter  class  is  the  burning  of 
wood.  Wood  is  composed  chiefly  of  carbon  and 
hydrogen,  with  a  very  small  proportion  of  oxygen. 
When  wood  burns  the  carbon  and  hydrogen  are  split 
apart,  the  carbon  uniting  with  oxygen  to  form  carbon 
dioxide,  CO2,  the  hydrogen  uniting  with  oxygen  to 
form  water,  H2O. 

Production  of  Carbon  Dioxide  and  Water  by 
Burning  Wood.  —  You  can  convince  yourself  of  this 

^  The  Bunsen  gas  jet  is  one  in  which  air  is  allowed  to  be  sucked 
in  with  the  gas  at  an  opening  a  few  inches  away  from  the  flame. 
The  result  of  this  intimate  admixture  of  air  and  gas  is  a  non- 
luminous  flame,  because  the  oxidation  is  very  complete  and  there 
are  no  luminous  particles  of  unoxidized  carbon  to  give  Ught. 
An  ordinary  luminous  flame  is  not  so  hot  and  a  certain  amount 
of  carbon  fails  to  bum  and  is  given  off  as  soot.  The  burners  of 
our  gas  stoves  are  modified  Bunsen  burners. 

D 


34  CHEMISTRY   FOR   NURSES 

by  a  very  simple  experiment.  Hold  a  burning 
match  mider  an  inverted  wide  test  tube  so  as  to 
catch  the  fumes.  Near  the  neck  of  the  tube  little 
beads  of  water  (condensed  steam)  are  formed  on 
the  glass  (ordinary  smoke  contains  a  considerable 
amount  of  moisture).  As  soon  as  the  match  stops 
burning,  quickly  turn  the  tube  right  side  up  and 
pour  some  lime  water  into  it.  The  lime  water  turns 
milky,  due  to  a  precipitate  of  calcium  carbonate 
formed  by  the  union  of  carbon  dioxide  with  calcium. 
(This  is  the  most  convenient  test  for  carbon  diox- 
ide.O 

The  Same  Substances  are  produced  by  the  Hu- 
man Body.  —  Thus  the  products  of  the  oxidation 
of  anything  composed  of  carbon  and  hydrogen  are 
carbon  dioxide  and  water.  This  is  just  as  true  of 
our  bodies  (which  are  composed  largely  of  carbon 
and  hydrogen)  as  it  is  of  the  match.  Just  as  CO2 
and  H2O  are  given  off  by  the  match,  they  are  given 
off  by  our  bodies.  This  can  be  easily  proved. 
Breathe  out  through  a  glass  tube  into  a  test  tube  of 
limewater;  the  limewater  quickly  becomes  cloudy 
from  the  CO2  of  the  breath.    The  water  produced 

^  It  is  due  to  this  reaction  that  a  bottle  of  limewater  left  un- 
stoppered  gradually  turns  cloudy  and  looses  its  strength  from 
the  traces  of  carbon  dioxide  in  the  air. 

/ 


ENERGY   AND    OXIDATION  35 

by  oxidation  in  our  bodies  is  given  off  as  sweat  and 
urine,  and  as  vapor  from  the  lungs. 

Why  we  need  Air.  —  During  respiration  the  air 
(which  is  practically  nothing  but  oxygen  diluted  with 
about  Jour  times  its  volume  of  nitrogen^)  is  drawn  into 
the  lungs  and  deprived  of  a  small  part  (about  5  %)  of 
its  oxygen.  In  exchange  it  receives  the  carbon  diox- 
ide which  the  body  has  to  get  rid  of.  The  oxygen 
that  is  absorbed  from  the  air  is  taken  up  by  the  red 
blood  corpuscles.  It  enters  not  into  firm  chemical 
union,  but  into  loose  combination  with  the  red  sub- 
stance called  haemoglobin  in  the  corpuscles.  Haemo- 
globin that  is  carrying  oxygen  in  this  way  is  bright 
red  in  color,  whereas  after  it  has  given  up  its  oxygen 
to  the  various  organs  and  tissues  it  is  deep  purple. 
This  is  the  cause  for  the  difference  in  color  of  blood 
flowing  from  arteries  and  that  flowing  from  veins. 

And  so  it  is  oxygen,  after  it  has  reached  the  tissues 
of  the  body,  that  liberates  the  energy  necessary  to 
produce  the  muscular  contractions,  the  warmth,  the 
nerve  actions,  and  the  thousand  other  manifestations 
of  life. 

^  It  also  contains  small  amounts  of  carbon  dioxide  and  water 
vapor  and  traces  of  a  number  of  other  gases. 


CHAPTER  V 
Acids 

Three  Principal  Kinds  of  Compounds.  —  As  there 
are  only  eighty  elements,  most  of  the  substances 
we  know  are  compounds.  Of  the  thousands  of  in- 
organic or  mineral  compounds  the  majority  belong 
to  one  of  three  classes  :  they  are  acids,  salts,  or  bases. 

The  acids  have  very  striking  characteristics  in 
common.  They  form  a  sharply  defined  group.  It 
might  be  well  to  begin  the  study  of  acids  by  examin- 
ing cautiously  ^  bottles  of  a  number  of  common  acids 
(hydrochloric,  sulphuric,  nitric,  acetic).  The  bottles, 
though  of  the  same  size  and  contents,  vary  greatly 
in  weight.  The  bottle  of  sulphuric  acid  is  sur- 
prisingly heavy. 

Taste.  —  If  you  dissolve  a  single  drop  of  any  of  the 
acids  in  a  glassful  of  water,  you  will  notice  that  a 
strong  sour  taste  has  been  given  to  the  water.  All 
acids  in  dilute  solution  taste  sour,  and  almost  all 
things  that  are  sour  are  acid.  Acetic  acid  is  what 
gives  the  sour  taste  to  vinegar,  citric  acid  to  lemon, 

*  Some  of  them  are  dangerous  poisons. 
36 


ACIDS  37 

phosphoric  acid  to  the  "  phosphate '^  at  the  soda 
water  fountain. 

Several  of  the  bottles  give  off  rather  irritating 
fumes  (hydrochloric,  nitric,  acetic  acids).  This  is 
because  these  acids  are  volatile  (easily  given  off  in  the 
gaseous  form). 

Physical  State.  Solubility.  —  Though,  for  con- 
venience, we  examine  the  acids  in  fluid  form,  or  at 
least  in  solution,  they  are  not  all  fluids  at  ordinary 
temperatures.  Some  are  solids  and  others  are  gases 
(hydrochloric  acid,  for  instance).  All  of  them  can 
be  made  either  solid,  fluid,  or  gaseous  by  suitable 
temperature  and  pressure.  They  are  all  easily 
soluble  in  water.  In  fact,  they  have  a  special  kind  of 
affinity  for  water  and  some  of  them  unite  with  it 
very  violently.  Thus  if  a  few  drops  of  sulphuric  acid 
are  carefully  ^  (drop  by  drop)  put  into  a  test  tube 
with  a  little  cold  water,  the  water  instantly  becomes 
very  hot. 

Let  us  try  the  effects  of  some  of  the  acids  on  cer- 
tain solid  substances  and  see  what  we  can  learn  about 
the  characteristics  and  composition  of  the  acids. 

^  Hold  the  tube  with  the  opening  pointed  away  from  your- 
self and  away  from  any  one  else.  This  is  a  safe  rule  for  all 
test  tube  experiments.  If  the  water  or  acid  is  hot  or  the  acid  is 
all  added  suddenly,  the  mixture  may  splutter  into  somebody's 
face. 


38  CHEMISTRY   FOR   NURSES 

Acids  attack  Metals.  —  Put  a  ten-cent  piece  in  a 
test  tube  with  some  strong  nitric  acid  and  heat  very 
gently.^  The  dime  dissolves  slowly  (as  can  be  de- 
termined later  by  seeing  the  corroded  surface)  and 
gives  off  little  bubbles  of  clear  gas.  The  solution 
turns  green  (due  to  the  fact  that  the  nitric  acid  dis- 
solves some  copper  out  of  the  dime ;  the  compounds 
of  copper  are  mostly  green).  Set  the  tube  aside  and 
a  little  later  you  can  return  to  it  and  perform  an 
experiment  that  will  convince  you  that  silver  is  also 
dissolved  in  it. 

Drop  a  very  small  piece  of  zinc  into  some  strong 
hydrochloric  acid.  The  zinc  dissolves  and  bubbles 
of  gas  come  away  from  it  in  a  lively  manner  as  though 
the  solution  were  boiling.  After  a  while  the  zinc 
disappears  entirely. 

Acids  form  Compounds  with  Metals.  —  In  both 
of  these  instances  a  solid  substance  has  been  dis- 
solved in  an  acid.  It  might  be  thought  that  the 
result  was  simply  a  solution  of  the  solid  in  the  fluid 
like  the  solution  of  salt  or  sugar  in  water.  But  this 
is  not  so.  If  we  evaporate  the  salt  or  sugar  solu- 
tion, we  get  back  simply  salt  or  sugar.  But  ij  we 
could  evaporate  the  tubes  in  which  the  dime  and  the 

1  If  heated  too  much,  large  volumes  of  intensely  irritating 
brown  fumes  are  given  off. 


ACIDS  39 

zinc  were  dissolved,  we  would  recover  not  copper,  or 
silver,  or  zinc,  but  a  green  compound  of  copper  called 
copper  nitrate,  a  crystalline  compound  of  silver 
called  silver  nitrate,  a  white  saltlike  poisonous  com- 
pound of  zinc  called  zinc  chloride.  Furthermore, 
if  we  could  examine  the  amount  of  acid  in  each  of  the 
tubes  before  and  after  the  addition  of  the  metal,  we 
would  find  that  the  acid  had  diminished.  The  acid 
used  itself  up  in  attacking  the  metal  and  forming 
the  new  compounds. 

The  most  striking  characteristic  of  the  acids,  then, 
is  their  power  of  decomposing  and  dissolving  certain 
other  substances,  with  the  formation  of  new  com- 
pounds. 

All  Acids  contain  Hydrogen.  —  Note  also  that 
in  both  experiments  huhhles  were  given  off.  If  we 
were  to  collect  and  examine  these  bubbles,  we  would 
find  in  both  instances  that  they  consisted  of  hydrogen 
gas.  Hence,  since  the  hydrogen  could  not  have 
come  from  the  dime  or  the  zinc,  it  must  have  come, 
in  each  instance,  from  the  acid.  Acids  contain 
hydrogen.^ 

And  now  (since  we  have  not  time  to  completely 

^  Not  all  acids  give  off  free  hydrogen  under  similar  conditions, 
but  there  are  other  methods  of  proving  that  all  acids  contain 
hydrogen. 


40  CHEMISTRY  FOR  NURSES 

analyze  the  acids)  let  us  see  what  we  can  learn  by 
examining  the  formulas  of  a  number  of  acids :  — 

Hydrochloric  Acid HCl 

Sulphuric  Acid H2SO4 

Nitric  Acid HNO3 

.  Carbonic  Acid H2CO3 

Phosphoric  Acid   • H3PO5 

Hydrocyanic  Acid HCN 

You  will  notice  that  besides  some  element  (chlorine, 
sulphur,  nitrogen,  etc.)  after  which  the  acid  is  named, 
and  besides  oxygen,  present  only  in  some  of  the  acids, 
all  the  acids  have  one  characteristic  in  common,  — 
they  all  have  at  least  one  hydrogen  atom. 

What  is  peculiar  about  the  Hydrogen  in  Acids  ?  — 
There  are  many  other  substances  that  have  hydro- 
gen atoms  in  their  molecules  (water,  for  instance) ; 
but  the  hydrogen  atom  in  the  acid  molecule  is  pecul- 
iar. It  is  loosely  attached,  so  that  you  may  think 
of  the  add  as  constantly  trying  to  get  rid  of  it.  But 
the  acid  can  only  get  rid  of  the  hydrogen  atom  on  one 
condition,  —  namely,  if  it  can  replace  the  gap  in  its 
structure  filled  by  the  hydrogen  atom  with  some 
other  atom  for  which  the  acid  has  a  greater  affinity. 
It  is  this  peculiarity  of  replaceable  hydrogen  atoms 
that  gives  all  the  acids  their  "acid"  characteristics. 


ACIDS  41 

Action  of  the  Nitric  Acid  on  Silver.  —  Thus  let 
us  take  the  first  experiment  above  (page  38)  —  the 
dissolving  of  silver  in  nitric  acid.  The  formula  for 
this  reaction  is :  —  « 

Ag        +     HNO3      =      AgNOs      +       H 

(Silver)  (Nitric  acid)  (Silver  nitrate)  (Hydrogen) 

What  happened  was  that  the  molecule  of  nitric  acid 
simply  threw  off  its  hydrogen  atom  and  replaced 
it  with  a  silver  atom.  The  excluded  hydrogen  was 
given  off  as  bubbles.  The  presence  of  dissolved  silver 
nitrate  can  he  proved  by  pouring  off  the  nitric  acid  in 
which  the  dime  has  partly  dissolved  and  adding  to 
it  some  hydrochloric  acid.  At  once  a  dense,  curdy 
white  precipitate  forms  and  sinks  to  the  bottom  of 
the  tube.  (A  precipitate  is  any  solid  that  is  formed 
as  the  result  of  a  chemical  reaction  in  a  fluid ;  usu- 
ally it  is  heavy  and  is  '^  precipitated  "  down  to  the 
bottom  of  the  tube.)  If  you  take  a  granule  of  silver 
nitrate  (such  as  you  are  already  familiar  with  in 
the  caustic  stick),  dissolve  it  in  water  and  add  a  little 
hydrochloric  acid,  you  will  get  the  same  kind  of 
white  precipitate.  The  formula  for  the  reaction 
by  which  the  precipitate  is  formed  is :  — 


AgNOa 

+         HCl       = 

HNO3    +  AgCl 

(Silver 

(Hydrochloric 

(Nitric               (Silver 

jQitrate) 

acid) 

acid)               chloride) 

42  CHEMISTRY   FOR  NURSES 

This  equation  shows  that  the  silver  has  left  its  at- 
tachment to  the  nitrogen-containing  molecule  (silver 
nitrate)  and  has  replaced  the  hydrogen  of  the  hydro- 
chloric acid.  In  this  test  there  was  a  contest  be- 
tween the  nitric  and  the  hydrochloric  acid  for  the 
possession  of  the  silver  atom.  The  hydrochloric 
acid  had  a  greater  affinity  for  silver  than  nitric  acid 
had,  and  the  resulting  compound,  silver  chloride,  being 
insoluble,  was  precipitated  down  as  a  solid. 

Similarly,  all  of  the  acids  have  particular  affinities 
for  certain  elements  or  combinations  of  elements 
and  combine  with  these  rather  than  with  others. 
The  substances  with  which  acids  combine  in  this 
way  are  chiefly  metals  and  the  combinations  or 
compounds  are  known  as  salts. 

There  are  Strong  and  Weak  Acids.  —  The  solvent 
powers  of  some  acids,  as,  for  instance,  the  strong 
mineral  acids,  hydrochloric,  hydrofluoric,^  nitric, 
sulphuric,  are  very  great.  Other  acids,  like  phos- 
phoric and  carbonic,  are  relatively  weak.  Another 
group  of  acids,  of  which  acetic  acid  is  an  example,  is 
known  as  organic  acids.  (See  chapter  on  organic 
chemistry.) 

^  Hydrofluoric  acid  is  so  powerful  a  solvent  that  it  dissolves 
even  glass,  and  hence  cannot  be  kept  in  glass  bottles.  It  is 
used  for  etching  on  glass. 


ACIDS  43 

Decomposing  Power  of  Acids.  —  Acids  not  only 
combine  with  those  substances  for  which  they  have 
chemical  affinity,  but  in  order  to  get  at  those  sub- 
stances, they  often  break  down  and  disintegrate  other 
molecules.  The  acids  are  therefore  very  powerful  de- 
composing agents.  To  illustrate  this  action,  drop  a 
small  splinter  of  wood  into  a  test  tube  of  sulphuric  acid 
and  warm  gently.  The  fragment  of  wood  rapidly 
becomes  charred  and  black  and  finally  disappears 
completely.-^ 

The  Litmus  Test.  —  There  is  a  very  simple  test 
for  the  presence  of  acid  in  any  solution,  —  namely, 
the  litmus  test.  Litmus  is  a  colored  substance  de- 
rived from  the  root  of  a  plant.  In  the  absence  of 
acid  it  is  purple  or  blue,  but  it  is  turned  bright  red  hy 
any  acid.  We  generally  use  pieces  of  paper  which 
have  been  soaked  in  litmus.  Dip  several  such  pieces 
of  paper  in  different  acids  and  all  of  them  turn  bright 
red.  It  will  help  you  to  remember  that  the  red 
color  of  litmus  indicates  acid,  if  you  remember  it  in 
connection  with  the  fiery  nature  of  acids. 

Acids  play  a  very  important  part  in  the  chemistry 
of  our  body.  The  most  important  acid  is  the  hy- 
drochloric acid  found  in  the  stomach  juice. 

^  Other  experiments  in  which  acids  are  used  to  split  mole- 
cules are  described  in  the  chapter  on  carbohydrates. 


CHAPTER  VI 
Bases 

As  peculiar  as  the  acids  and  yet  in  their  properties 
entirely  different;  in  fact  almost  exactly  the  opposite 
are  the  important  substances  called  bases  (also  called 
hydroxides  or  hydrates). 

Properties  of  Bases.  —  Let  us  examine  the  watery 
solutions  of  a  few  t3^ical  bases,  such  as :  — 

Sodium  hydrate  (caustic  soda) 
Potassium  hydrate  (caustic  potash) 
Ammonium  hydrate  (ammonia  water) 
Calcium  hydrate  (limewater) 

We  notice  that  when  applied  to  the  skin  they  give 
it  a  peculiar  soapy  feeling.  Some  of  them  (sodium 
potassium,  ammonium  hydrate^)  apphed  to  mucous 
membranes  are  strong  irritants  and  corrosive  poisons. 
When  diluted  well  (for  safety)  they  are  found  to  have 
an  unpleasant  soapy  taste.  Tested  with  litmus,  they 
are  found  to  do  exactly  the  opposite  to  acids,  — 
they  turn  litrrms  a  deep  blue  (whether  it  was  red  or 

*  These  are  the  bases  whose  characteristics  are  most  pro- 
nounced, —  the  strong  bases,  —  and  are  known  as  alkalies. 

44 


BASES  45 

purple  to  start  with).  This  is  the  best  test  for  bases ; 
anything  that  turns  Htmus  blue  is  basic  or  alkaline 
(the  two  terms  can  practically  be  regarded  as  inter- 
changeable). 

But  the  most  important  property  of  the  bases  is 
their  power  of  neutralizing  acids.  When  strong 
bases  and  acids  are  mixed  together  they  react 
violently  —  almost  explosively  —  with  each  other. 
If  potassium  hydrate,  for  instance,  is'  mixed  with 
hydrochloric  acid,  the  mixture  is  found  to  have  be- 
come very  hot,  and  if  enough  of  the  alkali  has  been 
added  the  peculiar  properties  of  the  acid  will  be 
found  to  have  entirely  disappeared. 

Decomposing  Powers.  — The  alkalies  have  power- 
ful dissolving  and  decomposing  properties  also,  though 
generally  to  a  less  extent  than  the  acids.  It  is  this 
property  that  makes  them  so  useful  as  cleansing 
agents  (ammonia,  washing  soda,  lye,  etc.).  Sodium 
and  potassium  hydrate  actually  have  some  decom- 
posing effect  (though  it  is  slight)  on  glass ;  so  that  if 
you  shake  up  a  bottle  of  one  of  these  substances  that 
has  been  standing  on  the  shelf  for  some  time,  you  will 
see  in  it  shavings  of  glass  dissolved  by  the  fluid  from 
the  inside  of  the  bottle. 

What  gives  these  bases  their  peculiarities?  Why 
do  they  neutralize  acids  ?    In  other  words,  what  is 


46  CHEMISTRY   FOR  NURSES 

their  chemical  composition?  We  can  find  out  best 
if  we  manufacture  some  alkali  ourselves.  Let  us 
make  some  sodium  hydrate. 

Sodium  combines  with  Water.  —  Throw  a  small 
piece  of  metallic  sodium^  into  a  beaker  of  water; 
it  floats  on  the  surface,  melts  (from  the  heat  of  the 
reaction),  rolls  about,  and  rapidly  disappears ;  at  the 
same  time  it  seems  to  evolve  bubbles  of  gas.  After 
the  sodium  has  disappeared  in  the  water  the  solution 
is  found  to  be  strongly  alkaline  and  to  have  all  the 
properties  of  caustic  soda  (sodium  hydroxide) ; 
and  if  the  gas  given  off  is  collected  in  an  inverted 
test  tube,  it  can  be  shown  to  be  hydrogen  gas.  In 
other  words,  sodium  hydrate  has  been  formed  by 
the  sodium  driving  some  of  the  hydrogen  out  of  the 
molecule  of  water.     This  is  shown  in  the  formula :  — 

Na     +    H2O      =      NaOH        +         H 

(Sodium)  (Water)  (Sodium  Hydrate)  (Hydrogen) 

So  in  general  bases  are  formed  by  the  combination 
of  some  metal  with  water;  and  in  fact  all  the  metals 
can  combine  in  this  way  to  form  hydroxides  (though 
most  of  them  do  not  unite  directly  and  violently 
as  sodium  does). 

1  Ordinarily  kept  in  a  bottle  of  petroleum  because  the  sodium 
oxidizes  rapidly  in  the  air  and  petroleum  is  one  of  the  relatively 
few  things  it  does  not  combine  with. 


BASES  47 

The  Atom  Group  OH.  —  Now  let  us  compare  the 
formula  of  sodium  hydrate  with  the  formulas  of  a 
couple  of  other  bases,  in  order  to  determine  what  the 
common  factor  is :  — 

Sodium  hydrate NaOH 

Potassium  hydrate KOH 

Ammonium  hydrate NH4OH 

Calcium  hydrate Ca(0H)2 

Magnesium  hydrate Mg(0H)2 

Iron  hydrate       Fe2(OH)6 

It  is  apparent  at  once  that  every  one  of  these  bases 
contains  the  atom  group  oxygen-hydrogen  (OH).  It 
is,  then,  this  OH  group,  combined  with  a  metal,^ 
that  makes  a  base. 

How  can  we  explain  the  Effect  of  Bases  on  Acids  ? 
—  In  the  OH  group  the  oxygen  and  hydrogen  atoms 
are  very  firmly  bound  together  so  that  when  the 
molecule  is  broken  up  in  any  chemical  change  the 
split  never  comes  between  them,  but  always  between 
the  OH  group  and  the  metal  atom.  The  metal 
atom  in  alkalies  (or  bases)  can  be  thought  of  as  always 
ready  to  be  split  off  and  replaced  by  a  hydrogen  atom, 

^Ammonium  hydrate  is  an  apparent,  not  real,  exception. 
Though  nitrogen  and  hydrogen  themselves  are  not  metals, 
when  united  in  ammonia  they  show  the  chemical  behavior  of 
a  metal. 


48  CHEMISTRY   FOR   NURSES 

just  as  the  hydrogen  atom  in  acids  is  always  ready 
to  be  replaced  by  a  metal  atom.  Thus  when  an 
alkali  and  an  acid  are  brought  together  the  condi- 
tions for  an  exchange  are  perfect.  Each  has  the 
atom  that  the  other  desires.  This  explains  the  neu- 
tralizing effect  of  bases  on  acids. 

Neutralization.  —  Take,  for  instance,  what  happens 
on  mixing  sodium  hydrate  with  hydrochloric  acid :  — 


NaOH 

+     HCl       = 

NaCl     +    H2O 

(Sodium 
hydrate) 

(Hydrochloric 

(Sodium               (Water) 

acid) 

chloride) 

Hydrochloric  acid  rejects  its  hydrogen  atom  in  ex- 
change for  the  metal  sodium  for  which  it  has  such  a 
strong  affinity.  The  alkali  (sodium  hydrate)  rejects 
its  metal  (sodium)  atom  in  exchange  for  the  hydrogen 
atom  freed  from  the  acid  and  forms  water.  You  see, 
then,  that  the  alkali  and  the  acid  on  being  mixed 
formed  sodium  chloride  (salt)  and  water.  The  salt 
is  neutral ;  it  is  neither  acid  nor  alkaline.  Litmus 
paper  dropped  into  it  does  not  change  color  at  all. 

This  experiment,  the  neutralization  of  an  acid  hy 
an  alkali^  and  the  resulting  formation  of  a  salt  is  simple 
and  can  be  performed  by  any  student.  Test  some 
weak  hydrochloric  acid  with  litmus  paper.  It  turns 
the  litmus  paper  bright  red.  Weak  sodium  hydrate 
turns  litmus  paper  blue.     Add  the  sodium  hydrate 


BASES  49 

solution  to  the  hydrochloric  acid  little  by  little,  test- 
ing with  litmus  paper  after  each  new  addition  to 
see  whether  the  solution  still  turns  the  paper  red. 
A  point  is  finally  reached  where  the  paper  no  longer 
changes.  This  is  the  neutral  point  and  the  solution 
is  no  longer  a  solution  of  acid  or  alkali,  but  a  solution 
of  sodium  chloride, —  ordinary  table  salt,  —  and  can 
be  safely  identified  by  the  sense  of  taste.  The  re- 
action which  has  taken  place  is  the  same  as  that 
shown  in  the  formula  above.  By  mixing  a  power- 
ful acid  and  a  powerful  .alkali  neutral,  harmless 
table  salt  has  been  formed. 

Bases  play  an  important  r61e  in  the  chemistry  of 
our  bodies.  The  blood  is  weakly  alkaline,  and  cer- 
tain of  the  digestive  juices  (bile  and  pancreatic  juice) 
are  decidedly  alkaline.     (See  chapter  on  digestion.) 


CHAPTER  VII 

Salts 

The  salts  are  the  third  great  group  of  compounds. 
They  are  more  numerous  in  the  world  and  play  a 
more  important  part  in  our  bodies  than  either  acids 
or  bases.  Although  they  have  no  true  nutritional 
value  (i.e.  supply  no  energy),  salts  are  absolutely  in- 
dispensable in  the  diet  of  all  animals.^ 

From  the  two  preceding  chapters  their  chemical 
composition  is  already  clear.  They  are  all  formed 
by  the  union  of  an  acid  with  a  metal.  The  metals 
which  combine  with  acids  to  form  salts  are  not  only 
the  familiar  metals  like  iron  and  silver,  but  also  cer- 
tain others  such  as  sodium,  potassium,  calcium,  and 
magnesium.  Besides  this  there  are  some  groups  of 
atoms,  themselves  not  metals,  but  which  combined 
act  like  metals.  The  most  important  of  these  is 
ammonia  (NH3).     In  the  study  of  organic  chemistry 

*  So  essential  is  salt  in  human  food  that  the  high  tax  put  on 
salt  by  a  rapacious  government  was  one  of  the  immediate  causes 
of  the  French  Revolution. 

60 


SALTS  51 

we  will  learn  that  there  are  many  other  such  com- 
binations. 

Salts  are  more  numerous  than  acids  because  for 
each  acid  there  are  as  many  different  salts  as  there 
are  metals  that  the  acid  can  combine  with.  Thus, 
for  instance,  consider  the  more  familiar  salts  of  the 
common  acids:  — 

Hydrochloric  acid  forms  chlorides. 

Sodium  chloride  (ordinary  table  salt) 
Potassium  chloride  (present  in  the  blood) 
Iron  chloride 


Calcium  chloride 
Ammonium  chloride 
Mercury  bichloride 


all  used  as  drugs 


Sulphuric  acid  forms  sulphates. 

Magnesium  sulphate  (Epsom  salts) 

Sodium  sulphate  (Glauber's  salts) 

Calcium  sulphate  (plaster  of  Paris) 

Copper  sulphate  (used  as  a  cauterizing  agent) 

Iron  sulphate  (used  as  a  drug) 

Zinc  sulphate  (disinfectant  and  cauterizing  agent) 

Nitric  acid  forms  nitrates. 

Sodium  nitrate 

Potassium  nitrate  (niter,  saltpeter)        „        ,        , 
r>-       i-i.      u  -x    X  all  used  as  drugs 

Bismuth  subnitrate 

Silver  nitrate 


52  CHEMISTRY   FOR   NURSES 

Carbonic  acid  forms  carbonates. 


used  medicinally 


Sodium  carbonal^e  (washing  soda) 
Sodium  bicarbonate 
Ammonium  carbonate 
Bismuth  subcarbonate 

Calcium  carbonate  (which  constitutes  marble,  chalk,  and 
limestone) 

Phosphoric  acid  forms  phosphates. 

Sodimn  phosphate  (present  in  the  blood,  used  as  a  drug) 
Calcium  phosphate  (which  constitutes  the  hard  part  of 

bones) 

There  are  innumerable  other  important  salts 
formed  by  the  action  of  various  acids  on  metals  in 
exactly  the  same  way. 

Bromides  and  Iodides.  —  Thus  the  elements  bro- 
mine and  iodine  are  very  much  like  the  element 
chlorine  and  form  acids  corresponding  in  name  and 
behavior  to  hydrochloric  acid.^  The  salts  formed 
from  bromine  are  known  as  hromides.  Sodium,  po- 
tassium, and  ammonium  bromides  are  important 
drugs.      The    salts    formed    from    the    iodine    are 

1  The  three  elements,  chlorine,  bromine,  and  iodine,  behave 
very  much  alike  and  constitute  a  group  of  elements  known  as 
the  halogen  elements  (because  their  salts  were  first  derived  from 
the  sea  or  from  seaweeds ;  the  word  "  halogen  "  is  a  Greek  word 
meaning  "  coming  from  the  sea")* 


SALTS  53 

known  as  iodides j  such  as  potassium  iodide  (KI), 
and  ammonium  iodide. 

Importance  of  Salts  in  the  Body.  —  Salts  play- 
many  and  varied  parts  in  our  body.  Thus  our 
blood  is  practically  salt  water  in  which  are  dissolved 
some  albumin  and  sugar  and  in  which  are  suspended 
or  floating  around  the  little  red  corpuscles  which  make 
the  blood  opaque  and  red. 

A  nurse  should  not  only  be  acquainted  with  the 
use  of  normal  salt  solution,  but  also  should  understand 
why  it  is  so  important  that  this  have  exactly  the 
right  strength,  namely,  0.6  %  to  0.9  %.  The 
reason  is  that  this  strength  is  the  same  as  the  strength 
of  the  salt  solution  of  the  blood. 

Effect  of  Distilled  Water  on  Blood.  —  It  is  in- 
teresting to  see  what  happens  to  blood  when  it  is 
^deprived  of  its  salt.  Take  a  test  tube  containing 
some  sheep's  blood  obtained  from  the  slaughter- 
house. It  is  opaque  and  dark  red  in  color  like  the 
blood  that  flows  from  a  vein  at  an  operation.^    Pour 

^  This  dark  color  incidentally  is  due  to  the  fact  that  the  blood 
has  been  standing  in  a  narrow  test  tube  open  only  to  the  air  at 
the  top  and  that  it  has  used  up  its  oxygen,  for  if  you  pour  a 
little  of  the  blood  into  another  test  tube  and  shake  it  up  well 
so  that  it  can'  absorb  oxygen  from  the  air,  it  turns  bright  red, 
but  is  still  opaque.  In  obtaining  the  blood  at  the  slaughter- 
house it  has  to  be  defibrinated,  i.e.  beaten  or  shaken  up  with 
glass  beads,  in  order  that  it  will  remain  fluid. 


64  CHEMISTRY   FOR   NURSES 

a  little  of  the  blood  into  a  test  tube  containing  some 
normal  salt  solution;  the  blood  retains  the  same 
opaque  appearance.  But  pour  some  of  the  blood 
into  a  test  tube  of  ordinary  water  or  of  distilled 
water  and  the  appearance  is  entirely  changed.  In  a 
moment  or  two  the  tube  instead  of  being  opaque 
becomes  perfectly  transparent. 

What  has  happened  is  that  in  the  absence  of  the 
salts  (or  what  is  the  same  thing,  when  the  salts  were 
greatly  diluted  so  as  to  be  present  in  only  a  little 
strength  as  compared  with  normal  salt  solution) 
the  red  blood  cells  became  completely  dissolved  and 
destroyed.  This  is  called  the  "  laking  "  of  blood, 
or  hcemolysis,  (Lysis  means  dissolving.)  It  is  be- 
cause of  the  danger  of  haemolysis  that  plain  or  dis- 
tilled water  cannot  be  used  for  intravenous  or  sub- 
cutaneous infusions,  but  saline  solution  has  to  be  used. 

What  is  true  of  the  red  blood  cells  is  also  true,  in 
large  part,  of  the  other  body  cells.  They  are  in- 
jured or  killed  by  contact  with  plain  water  or  with 
water  that  contains  insufficient  amount  of  salt. 
Actually  all  of  our  body  cells,  excepting  those  at 
the  surface  of  the  body,  are  bathed  and  live  in  salt 
solution. 

Functions  of  Special  Salts.  —  Each  of  the  salts 
has  important  special  functions  in  the  body.     Thus 


SALTS  55 

calcium  chloride  is  absolutely  essential  for  the  clotting 
of  blood;  if  we  did  not  have  it,  our  blood  would  never 
clot  and  we  should  bleed  to  death  from  the  slightest 
cut.  This  is  the  reason  why  calcium  compounds  are 
used  as  drugs  in  certain  diseases  in  which  the  blood 
does  not  clot  properly. 

Basic  and  Acid  Salts.  —  Not  all  salts  are  neutral 
in  reaction.  Some  are  alkaline  or  acid.  For  instance, 
the  carbonate  and  bicarbonate  of  soda  are  alkaline 
(and  are  used  medicinally  to  neutralize  excess  of 
hydrochloric  acid  in  the  stomach).  Their  alkalinity 
is  due  to  the  fact  that  they  consist  of  a  very  strong 
alkaline  metal  (sodium)  in  union  with  a  very  weak 
acid  (carbonic  acid).  On  the  other  hand  acid- 
sodium  phosphate  (the  best  drug  known  for  the 
purpose  of  making  the  urine  acid)  derives  its  acid 
properties  from  the  fact  that  in  its  formation  phos- 
phoric acid  does  not  get  all  of  the  sodium  it  could 
unite  with,  i.e,  is  incompletely  neutralized.  When 
phosphoric  acid  gets  all  the  sodium  it  can  combine 
with  it  forms  the  ordinary  sodium  phosphate  used 
as  a  laxative. 


CHAPTER  VIII 
Organic  Chemistry 

A  HUNDRED  years  ago,  when  people  were  first 
studying  such  things  earnestly,  it  was  noticed  that 
there  was  a  large  group  of  substances  entirely  distinct 
from  any  of  the  substances  we  have  mentioned  so 
far.  The  substances  of  this  group  were  all  derived 
directly  or  indirectly  from  plant  or  animal  organisms 
and  hence  were  called  "  organic  '^  (as  distinguished 
from  inorganic  or  mineral  substances). 

Organic  Matter  completely  Combustible.  —  They 
were  peculiar  in  that  they  were  all  easily  combustible, 
and  that  when  heated  they  would  first  char  (thus 
revealing  the  presence  of  carbon  as  one  of  their 
constituent  elements)  and  would  then  finally 
burn  up  completely  without  leaving  any  ash  or 
residue. 

(Compare  in  this  regard  the  behavior  of  a  typical 
mineral  substance,  table  salt,  and  a  typical  organic 
substance,  sugar.  Heat  a  grain  of  sodium  chloride 
and  a  grain  of  cane  sugar  side  by  side  on  a  platinum 
dish  over  a  Bunsen  flame.     The  sugar  turns  black 

56 


ORGANIC    CHEMISTRY  57 

and  disappears ;  the  salt  simply  melts,  and  remains 
as  a  solid  mass  after  cooling.) 

Elementary  Composition.  —  When  the  fumes  given 
off  were  examined  they  proved  to  consist  chiefly  of 
carbon  dioxide  and  water.  Sometimes  oxidized 
forms  of  nitrogen,  sulphur,  or  phosphorus  were 
obtained  also.  (It  is  noticed  that  all  these  elements 
are  such  as  burn  very  readily  and  have  volatile  oxida- 
tion products.)  Thus  it  came  to  be  recognized  that 
organic  compounds  are  made  of  carhon,  hydrogen,  and 
oxygen  with  occasionally  the  addition  of  nitrogen,  sul- 
phur, or  phosphorus^ 

But  here  progress  was  halted  for  a  long  while. 
The  organic  substances  seemed  to  defy  more  exact 
analysis.  And  especially  it  was  found  impossible  to 
manufacture  any  of  them  out  of  the  elements.  Ap- 
parently they  could  only  be  produced  by  the  living 
cell.  It  was  thought  that  this  must  be  due  to 
some  sort  of  "  vital  force ''  which  no  one  at 
that  time  thought  of  identifying  with  "  chemical 
affinity." 

Organic  Substances  not  limited  to  Living  Things. 
—  But  this  difficulty  was  presently  overcome. 
Beginning  with  the  epoch-making  synthesis  of  urea 
(a  nitrogen  containing  organic  substance  found  in 
urine)  from  the  elements,  by  Wohler  in  1828,  the 


68  CHEMISTRY   FOR   NURSES 

organic  substances  have  one  by  one  been  put  together 
by  scientists  in  the  laboratory.  The  old  idea  that 
organic  substances  are  peculiar  to  living  matter  had  to 
he  given  up.  And  to-day,  out  of  over  one  hundred 
thousand  organic  substances  known,  the  great 
majority  have  been  made  by  man  and  are  never 
found  in  living  organisms. 

What  is  S3mthetic  Chemistry  ?  —  This  wonderful 
development  of  synthetic  chemistry  —  of  the  mak- 
ing  of  new  and  ever  new  organic  compounds  — 
has  played  an  enormous  part  in  the  scientific  progress 
and  the  industry  of  modern  times.  To-day  we 
hardly  go  through  an  hour  of  our  lives  without  using 
some  of  these  marvelous  new  substances,  new  drugs, 
dyes,  flavors,  perfumes,  fabrics,  chemicals,  even 
foods. 

Biological  Chemistry.  —  Furthermore,  with  the 
development  of  organic  chemistry  it  was  possible  to 
begin  the  study  of  the  chemistry  of  life.  It  was 
found  that  the  body  is  a  chemical  laboratory  with 
all  sorts  of  intricate  changes  constantly  going  on. 
And  although  this  new  branch,  biological  chemistry, 
is  still  in  its  beginnings,  it  has  already  contributed 
greatly  to  our  understanding  not  only  of  the  normal 
processes  of  the  body,  but  also  of  the  changes  in  dis- 
ease.   There  is  a  whole  group  of  diseases,  such  as 


ORGANIC    CHEMISTRY  59 

gout,  diabetes,  uraemia,  due  solely  to  disturbances 
of  the  chemical  processes  of  the  body.  (These  are 
called  diseases  of  metabolism.) 

Different  Compounds  may  have  the  Same  Ele- 
ments. —  But  it  must  not  be  thought  that  this 
progress  was  easy.  The  deciphering  of  the  organic 
molecule  encountered  the  most  baffling  difficulties. 
For  not  only  was  it  found  that  most  organic  sub- 
stances were  made  of  the  same  few  elements,  but  it 
was  often  discovered  that  a  number  of  substances, 
each  one  having  properties  widely  different  from  the 
others,  would  all  on  analysis  turn  out  to  have  exactly 
the  same  number  of  carbon,  oxygen,  and  hydrogen 
atoms.  Thus  there  are  actually  eighty-two  different 
substances  known  having  the  formula  C9H10O3. 

How  is  it  possible  to  have  so  mxmy  different  sub- 
stances with  the  same  formula  f  The  answer  to  this 
riddle  dawned  gradually  on  the  chemists,  beginning 
about  1823  with  the  great  Liebig  and  Wohler.  It  is 
the  greatest  discovery  of  organic  chemistry,  namely, 
that  the  properties  of  a  substance  depend  not  only 
on  the  kind  and  number  of  its  atoms,  but  also  (and 
especially)  on  the  relative  positions  of  the  atoms  in 
the  molecule. 

Structural  Chemistry.  —  Thus  organic  chemistry 
has  become  a  study  of  the  architecture  of  the  mole- 


60  CHEMISTRY   FOR   NURSES 

cule.  Each  atom  has  as  definite  a  place  to  fill  in  the 
molecule  as  each  brick  and  beam  in  a  house.  Often 
if  a  single  important  atom  is  displaced,  the  whole 
molecule  disintegrates. 

The  unraveling  of  the  intricate  plans  of  the  organic 
molecules  has  proceeded  on  two  routes :  first,  by  the 
analysis  of  known  substances ;  and,  second,  by  put- 
ting already  known  substances  together  and  making 
new  substances. 

In  the  former  or  analytic  method  the  chemist  first 
finds  out  how  much  carbon,  hydrogen,  and  oxygen 
the  substance  has  and  what  simpler  compounds  are 
obtained  when  the  substance  is  decomposed.  And 
then,  knowing  the  combining  power  (valence)  of 
each  kind  of  atom,  he  tries  diagrams  of  all  the  pos- 
sible positions  in  which  the  atoms  could  be  linked 
together.  Often  he  is  unable  to  decide  which  of 
several  diagrams  corresponds  truly  to  the  molecule 
he  is  studying  until  he  has  succeeded  in  imitating 
the  molecule  by  synthesis  (building  up).  The  man 
who  builds  a  house  knows  where  all  the  beams  and 
stones  lie. 

Importance  of  Carbon.  —  As  more  and  more  of 
these  diagrams  were  deciphered  one  thing  became 
clear :  the  organic  molecule  is  built  up  around  the 
carbon  atom,  or  rather  around  groups  and  chains 


ORGANIC   CHEMISTRY  61 

of  carbon  atoms. ^    For  it  was  found  that  the  atom 
of  carbon  has  the  remarkable  property  (not  pos- 
sessed by  the  atom  of  any  other  element)  of  com- 
bining —  holding  hands  —  with  itself. 
So  the  four  valences  or  arms  of  the  carbon  atom, 

I 

— C — ,  are  really  the  key  to  all  the  complications 
of  organic  chemistry.    For  when  two  carbon  atoms 

I    I 

are  attached  to  each  other  thus,  — C — C — ,  they 

II 

need  use  only  one  each  of  their  valences.  This 
leaves  all  the  other  arms  free  to  combine  with  other 
atoms  of  carbon,  oxygen,  hydrogen,  or  other  elements. 
So  the  molecules  of  organic  substances  are  built  up 
around  chains  of  carbon  atoms  linked  together  like 
this :  — 

H 

H    H    H     O   H 

I      I      I      I      I 
H— 0— C— C— C— C— C— C  =  O 

I      I       I      I      I       I 
H    O    O    H    O    H 

III 
H    H  H 

(Plan  of  the  molecule  of  grape  sugar) 

*  For  this  reason  organic  chemistry  is  sometimes  described 
as  the  chemistry  of  the  compounds  of  carbon. 


62  CHEMISTRY   FOR   NURSES 

or  around  rings  of  carbon  atoms  like  this :  — 

H 


A 


H       ^\       H 


i 


c 


c 

k 

(Plan  of  the  molecule  of  phenol,  —  carbolic  acid  0 

Such  formulas,  of  course,  are  not  representations 
of  actually  seen  arrangements,  but,  like  the  atoms 
and  molecules  themselves,  are  theories;  they  are 
accepted  because  they  explain  the  behavior  of  the 
substances. 

Organic  Acids.  —  Many  organic  compounds  have 
either  acid  or  basic  properties  like  the  inorganic  acids 
and  bases  referred  to  in  earlier  chapters  (Chapters 
V  and  VI).     The  acid  properties  are  all  due  to  the 

^  Substances  built  up  on  this  "  ring  "  plan  belong  to  a  group 
known  as  the  aromatic  group  of  substances,  because  of  the  strong 
odors  or  tastes  of  many  of  them.  Some  other  members  of  the 
group  are  camphor,  menthol,  benzol,  turpentine,  quinine, 
salicylic  acid,  benzoic  acid,  phenacetine,  indigo. 


ORGANIC   CHEMISTRY  63 

same  replaceable  hydrogen  atom  which  gives  the  acid 
properties  to  the  mineral  acids.  And,  similarly,  when 
these  atoms  are  replaced,  salts  result.  Thus  from 
the  well-known  organic  acids,  acetic  acid  (vinegar), 
lactic  acid  (sour  milk),  tartaric  acid  (grapes,  baking 
powder),  oxalic  acid  (many  vegetables),  citric  acid 
(lemons)  are  formed  organic  salts  known,  respectively, 
as  acetates,  lactates,  tartrates,  oxalates,  citrates. 
The  most  important  of  the  organic  acids  are  the  so- 
called  '^  fatty  acids'-^  (see  Chapter  on  Fats),  such  as 
acetic,  butyric,  oleic  acids. 

Organic  Bases.  —  Among  the  organic  substances 
with  more  or  less  basic ,  properties  (i.e.  neutralizing 
acids)  the  alcohols  are  very  important.^  They  have 
the  same  atom  group,  OH,  which  we  found  in  the  in- 
organic bases  like  sodium  hydrate  (NaOH)  or  am- 
monium hydrate  (NH4OH).  Some  of  them  have 
several  of  these  OH  groups.  Thus  ordinary  glycerin 
is  an  alcohol  with  three  OH  groups  in  its  molecule 
so  that  it  can  neutralize  three  different  acid  mole- 
cules at  one  time.     (See  Chapter  on  Fats.) 

Another  group  of  organic  bases  is  the  alkaloids,  — 
substances  like  morphine,  codeine,  cocaine,  strych- 

^  For  reasons  which  cannot  be  gone  into  here  the  alcohols  do 
not  turn  Utmus  blue  and  lack  certain  other  "  alkaline  "  prop- 
erties. 


64  CHEMISTRY   FOR   NURSES 

nine,  and  atropine,  —  derived  from  plants  and  used 
as  drugs.  They  all  form  salts  such  as  morphine  sul- 
phate, cocaine  hydrochloride,  etc.^ 

There  are  three  groups  of  organic  substances 
which  dominate  the  chemistry  of  food  and  of  the 
body.  These  are  carbohydrates,  fats,  and  proteids. 
They  will  be  discussed  in  the  succeeding  chapters. 

1  See  Blumgarten,  "  Materia  Medica  for  Nurses." 


CHAPTER  IX 

Carbohydrates 

The  sugars  and  starches  form  a  large  part  of  the 
staple  food  of  man.  There  are  many  different  kinds, 
but  they  all  resemble  each  other  both  as  to  chemical 
constitution  and  as  to  the  functions  they  perform  in 
the  living  organism.  On  this  accoimt  they  are  all 
grouped  together  under  the  name  of  carbohydrates. 
The  carbohydrates  are  the  first  of  the  three  great 
classes  of  food  and  body  substances  which  we  are  to 
study.^ 

Of  What  Use  are  Carbohydrates?  —  The  prin- 
cipal function  of  carbohydrates,  both  in  plants  and 
animals,  is  to  provide  energy  by  being  oxidized.  There 
are  many  circumstances,  however,  under  which  both 
plants  and  animals  need  to  store  away  energy  for 
future  consumption.  Under  these  circumstances 
the  plants  store  away  their  energy  chiefly  in  the  form 
of  carbohydrates  J  the  animals  chiefly  in  the  form  of 

^  This  book  is  intended  to  give  the  principles  underlying  the 
study  of  dietetics.  For  a  practical  discussion  of  different  foods 
see  Mclsaacs,  "  Hygiene  for  Nurses,"  Chapter  on  Foods. 

p  66 


66  CHEMISTRY    FOR   NURSES 

fat.  Thus  the  starch  packed  away  in  the  roots,  the 
sugars  treasured  up  in  the  fruits,  are  reserves  on 
which  the  plant  draws  in  time  of  need.  In  the  ani- 
mal body  the  fat  performs  this  storehouse  function, 
and  carbohydrates,  though  they  form  a  large  part 
of  the  food,  are  used  up  almost  as  quickly  as  they  are 
taken. 

What  Elements  form  Carbohydrates  ?  —  A  glance 
at  the  chemical  formulas  of  carbohydrates  will  show 
why  they  serve  so  well  as  sources  of  energy.  They 
are  all  composed  of  carbon,  hydrogen,  and  oxygen, 
and  the  hydrogen  and  oxygen  are  always  present 
in  the  same  proportion  as  in  water,  namely,  two 
atoms  of  hydrogen  to  every  one  of  oxygen.  Thus 
grape  sugar  is  C6H12O6;  cane  sugar,  C12H22O11. 
Note  this  ratio,  —  twice  as  many  hydrogen  as 
oxygen  atoms ;  it  is  significant.  It  means  that  the 
hydrogen  is  enough  to  exactly  satisfy  the  oxygen 
already  in  the  molecule ;  thus  all  the  carbon  can  com- 
bine with  oxygen  and  provide  energy.  The  products 
of  the  oxidation  are  therefore  carbon  dioxide  (CO2) 
and  water. 

Three  Classes  of  Carbohydrates.  —  There  are  three 
chief  classes  of  carbohydrates  :  (1)  the  simple  sugars  or 
monosaccharides,  very  soluble  and  digestible  and  hav- 
ing always  six  carbon  atoms  to  the  molecule ;  (2)  the 


CARBOHYDRATES  67 

double  sugars  or  disaccharides,  almost  as  soluble  and 
digestible  and  having  always  twelve  carbon  atoms; 
and  (3)  the  polysaccharides  or  complex  carbohydrates, 
dissolved  and  digested  with  much  more  difficulty 
and  having  large  numbers  of  carbon  atoms  to  the 
molecule. 

I.     MONOSACCHARIDES    (siMPLE    SUGARs) 

Dextrose  (glucose,  grape  sugar) 
Levulose  (fruit  sugar,  fructose) 

Glucose  is  found  in  plants  and  fruits  as  well  as  in 
the  blood;  the  muscles,  and  the  liver  of  animals. 

Levulose  is  found  in  sweet  fruits  and  is  especially 
abundant  in  honey. 

The  Arrangement  of  the  Atoms  determines  the 
Properties  of  the  Substance.  —  There  is  no  class  of 
substances  which  illustrate  more  beautifully  and 
simply  than  the  monosaccharides  how  a  slight  differ- 
ence in  the  position  of  the  atoms  in  the  molecule 
may  change  the  nature  of  a  substance.  All  the 
monosaccharides  ^  have  exactly  the  same  composi- 
tion ;  they  are  all  C6H12O6.  Not  only  this,  but  they 
are  all  built  on  the  same  general  plan,  —  a  chain  of 

1  There  are  many  more  than  the  two  monosaccharides  men- 
tioned, but  here,  as  under  each  heading,  only  the  examples  that 
^re  of  practical  importance  are  given. 


6S  CHEMISTRY   FOR   NURSES 

six  carbon  atoms,  to  whose  side  arms  (valences)  are 
attached  the  hydrogen  and  oxygen  atoms.  Never- 
theless, the  different  sugars  differ  from  each  mother 
in  all  their  properties. 

Thus  consider  grape  sugar  and  fruit  sugar.  Grape 
sugar  (dextrose)  is  the  form  in  which  sugar  exists 
in  the  human  body ;  it  circulates  in  the  blood  and 
is  found  in  the  muscles;  if  it  is  injected  into  the 
body,  it  is  all  utilized  (unless  injected  in  very  great 
excess).  Levulose,  on  the  other  hand,  is  foreign  to 
the  blood  and  tissues.  If  it  is  injected,  most  of  it  is 
promptly  thrown  out  again  by  the  kidneys.  It  is 
much  sweeter  than  dextrose.  Likewise  the  two 
differ  markedly  in  their  chemical  properties.^  Yet 
compare  the  plan  of  grape  sugar  and  of  fruit  sugar : 

H 


H    H    H    O    H 

I 


-C  =  0 


H    O    O    H    O    H 

I  I 

H  H 


k 


Grape  Sugar 

1  If  a  beam  of  a  peculiar  kind  of  light  called  polarized  light 
passes  through  a  dextrose  solution,  it  is  twisted  to  the  right,  if 
through  a  levulose  solution,  to  the  left.  This  remarkable  prop- 
erty, which  is  due  to  the  conformation  of  the  molecules,  is  used 
in  detecting  and  measuring  sugars  and  other  substances. 


CARBOHYDRATES  O^ 

H 

I 
H    H    H    O  H 

H— O— C— C— C— C— C— C— O— H 

I      I       I       I      II      I 
H    O     O    H    O    H 

u 

Fruit  Sugar 

The  two  are  so  nearly  alike  that  by  simply  shifting 
the  position  of  two  hydrogen  atoms  they  could  be 
made  identical. 

The  properties  of  the  simple  sugars  will  be  dis- 
cussed together  with  those  of  the  double  sugars. 

n.    DISACCHARIDES 

Sucrose  (cane  sugar  ^) 
Lactose  (milk  sugar) 
Maltose  (malt  sugar) 

Cane  sugar  occurs  not  only  in  the  sugar  cane,  but 
in  beets,  maple  sugar,  honey,  and  many  other  vege- 
table products. 

Milk  sugar  is  found  in  the  milk  of  all  mammals. 
It  is  less  sweet  and  less  soluble  than  cane  sugar. 

^  Sucrose  (sometimes  called  saccharose)  should  not  be  con- 
fused with  saccharine,  an  intensely  sweet  substance  used  for 
flavoring  sugar-free,  diabetic  foods.  Saccharine  is  not  a  car- 
bohydrate and  is  not  nutritious.  It  is  chemically  one  of  the 
aromatic  substances  (like  carbolic  acid),  but  is  not  poisonous. 


70^  CHEMISTRY   FOR   NURSES 

Maltose  is  a  sugar  derived  artificially  from  starches 
by  digestion  or  chemical  splitting.  Ordinarily,  it  is 
made  from  starch  by  the  digestive  action  of  a  sub- 
stance obtained  from  sprouting  barley  grains  and 
called  malt  extract  or  diastase.  How  this  substance 
works  will  be  explained  in  the  Chapter  on  Digestion. 
Maltose  is  a  valuable  food  and  is  the  chief  constit- 
uent of  such  preparations  as  malt  soup,  Mellin's 
food,  malted  milk. 

The  double  sugars,  or  disaccharides,  are  so  called 
because  their  molecules  consist  of  two  simple  sugar 
molecules  linked  together;  so  that  the  formula  of 
all  disaccharides  is  C12H22O11.  The  various  double 
sugars  differ  from  each  other  in  being  composed  of 
different  simple  sugars.  Thus  the  molecule  of  cane 
sugar  contains  a  molecule  of  dextrose  and  one  of 
levulose,  while  the  molecule  of  maltose  contains 
two  dextrose  molecules.^ 

1  After  the  student  is  acquainted  with  FehUng's  test  for  sugar 
(see  below,  page  74)  a  simple  experiment  can  be  done  to  prove 
that  double  sugars  contain  simple  sugar  molecules.  It  happens 
that  cane  sugar,  a  disaccharide,  does  not  give  Fehling's  test, 
while  all  the  simple  sugars  do.  Hence  if  cane  sugar  can  be  split 
into  its  two  constituent  molecules,  dextrose  and  levulose,  these 
will  give  Fehling's  test. 

First  boil  some  cane  sugar  with  Fehling's  solution :  there  is  no 
reduction.  Now  put  a  Uttle  cane  sugar  in  a  test  tube  with  some 
strong  hydrochloric  acid  and  heat  gently.    NeutraHze  the  acid 


CARBOHYDRATES  71 

PROPERTIES  OF  THE  SUGARS 

The  simple  and  the  double  sugars  have  certain 
properties  more  or  less  in  common.  They  are  all 
very  soluble;  they  can  be  obtained  as  crystals;  they 
all  taste  more  or  less  sweet;  they  are  very  digestible 
and  highly  nutritious.  Perhaps  their  most  interest- 
ing characteristic  is  their  property  of  undergoing 
fermentation, 

FERMENTATION 

The  lowly  and  simple  forms  of  life,  the  bacteria, 
the  molds y  and  the  yeasts,  have,  after  all,  the  same  basic 
requirements  as  the  higher  forms.  They  must 
breathe  and  they  must  feed.  Very  many  of  them  are 
specially  adapted  to  use  carbohydrates  as  their  chief 
food.  In  so  feeding  they  do  the  same  thing  as  the 
higher  organisms,  they  oxidize  the  carbohydrates. 
And  the  final  products  of  this  oxidation  are  the  same, 
—  carbon  dioxide  and  water.  This  decomposition  of 
carbohydrates  by  bacteria  or  yeasts  is  known  as 
fermentation. 

(see  page  48)  with  some  30  %  sodium  hydrate  and  then  test  a 
little  of  the  fluid  with  FehHng's  solution.  The  result  is  complete 
reduction.  The  acid  has  split  the  double  molecule  to  its  com- 
ponent simple  sugars.  The  same  kind  of  molecule  splitting 
happens  in  the  digestion  of  every  disaccharide.  (See  Chapter  on 
Digestion.) 


72  CHEMISTRY   FOR   NURSES 

Experiment  showing  Action  of  Yeast  on  Dextrose. 

—  To  demonstrate  fermentation,  mix  a  little  piece 
of  baker's  yeast  with  some  glucose  solution,  and  with 
the  mixture  fill  one  of  the  small  tubes  known  as  Ein- 
horn  fermentation  tubes.  This  is  a  U-shaped  glass 
tube,  one  limb  of  which  is  closed  on  top  so  as  to  col- 
lect gas  bubbles.  Let  the  tube  stand  in  a  warm  place 
for  a  day  and  then  examine  it.  Bubbles  of  carbon 
dioxide  will  have  collected  in  the  closed  end  of  the 
tube,  and  the  amount  of  this  gas  can  easily  be  meas- 
ured off  from  a  scale  engraved  in  the  outside  of 
the  tube.  From  this  amount  we  can  easily  tell  how 
much  sugar  was  originally  dissolved;  for  as  each 
carbohydrate  molecule  has  six  carbon  atoms, 
and  each  carbon  atom  gives  rise  to  one  carbon 
dioxide  molecule  when  fermented,  the  amount  of 
carbon  dioxide  is  proportional  to  the  amount  of 
sugar.^ 

The  production  of  gas  bubbles  by  yeast  growing 
on  carbohydrates  is  the  principle  underlying  the 
'^  raising  '^  or  leavening  of  bread. 

By-products  of  Fermentation.  —  But  our  interest 
in  fermentation  does  not  stop  here.     What  is  impor- 

^This  method  is  actually  used  to  estimate  approximately 
the  amount  of  sugar  in  the  urine  of  diabetes  cases.  The  scale 
on  the  Einhorn  tube  reads  directly  in  percentages  of  sugar. 


CARBOHYDRATES  73 

tant  about  fermentation  is  not  so  much  the  end  products 
as  the  by-products.  For  in  fermentation  (just  as  in 
the  body)  substances  are  not  at  once  and  completely 
oxidized,  but  the  molecules  are  first  broken  up  into 
partly  oxidized  fragments,  and  then  these  are  further 
oxidized  to  carbon  dioxide  and  water. 

Alcoholic  Fermentation.  —  These  intermediate 
products  are  different  for  each  kind  of  carbohydrate 
and  for  each  kind  of  bacterium  or  yeast.  Thus  the 
chief  by-product  of  many  kinds  of  fermentation  is 
alcohol;  and  each  kind  of  alcoholic  beverage  is  the 
result  of  fermentation  of  the  carbohydrates  in  some 
particular  kind  of  grain  or  fruit,  by  a  microorganism 
that  is  specially  adapted  for  the  purpose.^ 

Lactic  Acid  Fermentation.  Vinegar.  —  The  by- 
products in  many  kinds  of  fermentations  are  organic 
acids,  such  as  acetic,  lactic,  and  butyric  acids.  Thus 
in  the  manufacture  of  kumiss  and  matzoon  and  of 
various  kinds  of  sour  milk  and  cheese  lactic  acid  is 
produced.  The  production  of  vinegar  is  an  acetic 
fermentation  {i.e.  a  fermentation  by  bacteria  which 

1  If  the  wrong  germ  gets  in,  the  wine  spoils.  Thus  the  whole 
modern  science  of  bacteriology  started  in  the  effort  of  Louis 
Pasteur  to  discover  why  the  wine  soured  in  a  certain  wine-grow- 
ing district  in  France.  The  discovery  of  a  germ  as  the  cause  of 
a  "  wine  disease  "  led  him  to  search  for  germs  as  possible  causes 
of  human  disease. 


74  CHEMISTRY   FOR   NURSES 

produce  acetic  acid).  There  are  hundreds  of  manu- 
facturing processes  which  depend  on  various  kinds 
of  fermentation. 

Gastro-intestinal  Fermentation.  —  When  fermen- 
tations occur  in  the  intestinal  tract  the  acids  pro- 
duced are  often  very  irritating  and  cause  digestive 
disturbances.  Our  chief  means  of  combating  such 
troubles  is  careful  regulation  of  the  carbohydrates 
in  the  diet. 

TESTS   FOR  SUGARS 

It  is  often  necessary  to  test  for  sugar.  This  is 
done,  for  instance,  in  order  to  determine  whether  a 
patient  has  glycosuria  (glucose  in  the  urine,  the  chief 
sjonptom  of  diabetes).  The  fermentation  test  with 
yeast  described  above  is  frequently  used. 

More  delicate  and  reliable  than  the  fermentation 
test  are  chemical  tests  based  on  the  great  avidity 
of  certain  sugars  for  oxygen.  These  sugars  have  the 
power  of  reduction f  i.e.  the  power  of  taking  some  of 
the  oxygen  away  from  other  compounds.  The  best 
known  of  these  tests  is  the  Fehling^s  test,  in  which 
the  sugar  is  made  to  "  reduce  ''  an  oxidized  copper 
salt  to  a  form  containing  less  oxygen. 

Fehling's  Test  for  Sugar.  —  Fehling's  test  is  per- 
formed with  two  solutions.    The  first,  known  as 


CARBOHYDRATES  75 

Fehling's  copper  solution,  is  a  light  blue  solution  of 
copper  sulphate.  The  other  is  a  strong  alkaline 
solution  called  Fehling's  alkaline  solution.  Equal 
quantities  of  the  two  are  mixed  together  in  a  test 
tube;  the  result  is  a  beautiful  deep  blue  fluid;  if 
this  solution  is  boiled,  it  retains  its  color.  But  if 
a  little  dextrose  (or  some  urine  containing  dextrose) 
is  added,  and  the  mixture  is  boiled  again,  a  thick, 
reddish  yellow  precipitate  forms.  This  is  reduced 
copper  oxide,  —  a  copper  compound  from  which 
some  of  the  oxygen  has  been  withdrawn. 

Sometimes  in  pregnant  or  nursing  women  milk 
sugar  appears  in  the  urine.  This  gives  the  same 
reduction  in  Fehling's  test  as  does  dextrose.  But 
as  lactose  is  not  fermented  by  yeast,  while  dextrose 
is,  we  have  only  to  do  the  fermentation  test  to  make 
sure  that  the  patient  has  not  diabetes. 

III.     POLYSACCHARIDES 

Starch 

Dextrin 

Glycogen  (animal  starch) 

Cellulose  (vegetable  fiber) 

The  polysaccharides  are  important  foods.  Their 
molecules  contain  great  numbers  of  sugar  molecules 
compactly  linked  together.    When  these  large  mole^ 


76  CHEMISTRY   FOR  NURSES 

cules  enter  the  digestive  tract  they  have  to  be  broken 
down  to  simple  sugars  before  they  can  be  used  for 
nutrition.     (See  Chapter  on  Digestion.) 

Proof  that  Starch  is  made  up  of  Sugar  Mole- 
cules. —  The  fact  that  the  polysaccharide  molecule 
is  really  built  up  of  sugar  molecules  can  be  demon- 
strated by  boiling  some  starch  paste  a  few  minutes 
in  hydrochloric  acid,  then  cooling  and  neutralizing 
the  acid  with  sodium  hydrate.  Before  the  boiling 
the  starch  fails  to  give  any  change  with  Fehling's 
test.  After  boiling  it  completely  reduces  Fehling's 
solution.  Glucose  and  maltose  have  been  produced 
from  the  starch. 

Why  Starch  needs  Cooking.  —  Starch  is  the  form 
in  which  most  plants  store  up  their  energy.  It  is 
not  soluble  in  water,  but  can  be  made  into  a  paste 
by  boiling.  In  its  natural  form  it  occurs  in  little 
granules  of  microscopic  size.  Under  the  microscope 
each  granule  is  seen  to  be  composed  of  concentric 
layers  like  an  onion.  The  layers  are  separated,  it  is 
believed,  by  very  fine  films  of  another  carbohydrate, 
cellulose,  which  is  extremely  difficult  of  solution 
or  digestion.  This  is  the  reason  that  it  is  so  impor- 
tant that  starchy  things  prepared  for  human  food 
be  well  cooked :  in  the  process  of  cooking  the  heat 
splits  open  the  starch  granules  and  the  starch  be- 


CARBOHYDRATES  77 

tween  the  layers  of  cellulose  can  be  reached  by  watei 
or  by  digestive  juices. 

Iodine  Test  for  Starch.  —  If  a  drop  of  any  solu- 
tion containing  iodine  is  added  to  starch,  a  deep  blue- 
black  color  is  produced.  This  color  can  be  shown 
by  adding  tincture  of  iodine  to  starch  direct  or  by 
putting  a  drop  of  it  on  the  cut  surface  of  a 
potato  or  piece  of  bread.  The  color  is  not  given 
by  any  other  substance,  and  gives  us  a  valuable 
method  of  detecting  starch.  For  instance,  with 
iodine  we  can  tell  whether  gluten  foods,  claimed 
to  be  starch  free,  are  really  so. 

Dextrin  (a  polysaccharide  not  to  be  confused  with 
dextrose,  a  simple  sugar)  is  a  product  of  the  begin- 
ning chemical  splitting  up  of  starch  by  acids,  or  the 
partial  digestion  of  starch  by  malt  extract  or  diges- 
tive juices.  Thus  it  is  seen  that  as  the  starch  mole- 
cule is  split  up  there  are  produced  the  successively 
smaller  fragments,  dextrin,  maltose,  and  dextrose. 
The  molecules  of  dextrin  contain  still  a  great  num- 
ber of  sugar  molecules,  but  not  nearly  so  many  as 
starch  itself.  It  is  more  soluble  than  starch,  more 
digestible,  and  it  does  not  give  a  blue  color  on  the 
addition  of  iodine,  but  either  a  mahogany-brown  color 
or  no  color  at  all.  It  is  a  valuable  food.  It  has  a 
pasty  consistency  and  is  often  used  as  a  gum. 


78  CHEMISTRY   FOR   NURSES 

Glycogen  (animal  starch)  is  found  in  the  liver  and 
muscles  and  is  the  form  in  which  carbohydrates  are 
temporarily  stored  in  animals.  It  is  on  account  of 
the  large  amount  of  glycogen  in  liver  that  liver  is 
forbidden  for  those  diabetic  patients  who  have  to  be 
on  a  strict  carbohydrate-free  diet.  Glycogen  is  very 
similar  to  starch  in  its  appearance  and  properties, 
but  is  more  soluble. 

Cellulose  is  the  carbohydrate  which  forms  the 
fibrous  or  woody  part  of  plants.  It  is  the  chief  con- 
stituent of  cotton,  linen,  and  paper.  It  is  very  insol- 
uble and  (by  human  beings)  very  indigestible ;  but 
the  digestive  tracts  of  the  herbivorous  (plant-eating) 
animals  break  it  down  to  its  constituent  mono- 
saccharides and  utilize  it  as  food.  It  is  possible  now 
to  make  human  food  (glucose)  from  it  by  treating  it 
with  strong  acids.  (This  can  be  demonstrated  by 
heating  a  little  piece  of  wood  with  sulphuric  acid, 
cooling  and  neutralizing  and  testing  for  sugar  with 
Fehling's  solution.) 

In  the  study  of  digestion  it  will  be  seen  that  the 
same  breaking  down  of  complex  food  molecules  into 
simpler  molecules,  which  in  the  test  tube  we  can  bring 
about  with  the  aid  of  powerful  reagents,  can  be  per- 
formed in  the  body  by  means  of  such  harmless  sub- 
stances as  saliva  and  pancreatic  juice. 


CHAPTER  X 
Fats 

Fat  a  Source  of  Energy.  —  As  explorers  go  toward 
the  north  and  south  poles  they  notice  that  plant 
life  gradually  dies  out.  Animals  venture  much 
farther  into  these  frozen  regions  than  plants  do. 
And  one  thing  is  common  to  all  these  animals  that 
brave  the  polar  cold :  their  bodies  are  saturated  with 
fat.  It  is  this  that  makes  life  possible  for  them,  not 
(as  is  often  thought)  by  providing  a  warm  coating, 
but  by  supplying  a  constant  source  of  highly 
combustible  fuel  to  keep  up  the  body  temperature. 
The  Eskimo  knows  the  warmth-giving  value  of  fat 
and  lays  up  large  stores  of  it  for  his  winter  sus- 
tenance. 

The  Storing  away  of  Energy.  —  Just  as  carbohy- 
drates are  the  principal  form  in  which  plants  store  up 
their  reserve  energy,  fats  are  the  arsenal  of  chemical 
energy  in  the  animal  body.  Animals  may  simply  lay 
away  in  their  tissues  the  fat  which  they  eat  and  do 
not  need  for  oxidation  at  the  time,  or,  as  a  result  of 

79 


80  CHEMISTRY    FOR   NURSES 

the  wonderful  chemical  transformations  the  body 
can  perform,  they  may  convert  other  forms  of 
nourishment,  such  as  carbohydrates  and  proteids, 
into  fats.  Persons  who  eat  much  sugar  (candy), 
for  instance,  tend  markedly  to  adiposity.  The 
sugar  in  excess  of  the  actual  energy  needs  of  the 
body  is  retained  not  in  the  form  of  sugar,  but  of 
fat. 

Fats  give  more  Heat  than  do  Carbohydrates.  — 
Indeed  in  this  regard  the  chemistry  of  the  animal 
body  is  more  cunning  than  that  of  the  plant.^  Fats, 
weight  for  weight,  have  over  twice  as  much  heat-giving 
power  as  carbohydrates;  nine  calories  per  gram  as 
compared  with  four.  Where  does  this  energy  come 
from?  From  the  unoxidized  carbon  and  hydrogen 
of  the  fat  molecule,  of  course.  For  though  fats  are 
made  of  the  same  elements  as  carbohydrates,  — 
namely,  carbon,  hydrogen,  and  oxygen,  —  the  rela- 
tive amount  of  oxygen  is  much  smaller,  so  that  the 
carbon  and  hydrogen  atoms  can  take  up  more 
oxygen  and  hence  provide  more  energy  than  can  the 
carbohydrate  niolecule. 

1  It  must  not  be  supposed  that  plants  have  no  fats  or  that 
animals  have  no  carbohydrates.  Some  plants  have  large 
amounts  of  fat ;  think  of  peanut  butter,  cocoa  butter,  cotton- 
seed oil,  and  olive  oil.  Cereals  have  small  and  nuts  often  large 
amounts  of  fat. 


FATS  81 

CHEMICAL  COMPOSITION  OF  FATS 

It  is  worth  trying  to  understand  something  of  the 
chemical  structure  of  fats  because  of  the  help  that 
knowledge  will  give  us  in  the  study  of  soaps  and  of 
fat  digestion. 

What  are  Fats  Composed  Of  ?  —  Fats  are  comhina- 
tions  of  fatty  acids  and  glycerin.  When  the  fat  mole- 
cule is  split  apart  by  strong  reagents  or  by  digestion, 
it  breaks  up  into  these  two  constituents.  (An 
experiment  showing  the  production  of  fatty  acids 
by  the  splitting  of  fats  is  described  in  the  Chapter  on 
Digestion.     See  page  109.) 

There  is  very  little  Oxygen  in  Fatty  Acids.  — Fatty 
acids  (of  which  there  are  a  great  many)  contain 
in  their  molecules  varying  numbers  of  carbon  and 
hydrogen  atoms,  but  no  matter  how  many  carbon 
and  hydrogen  atoms,  only  two  oxygen  atoms. 
Thus  from  acetic  acid,  C2H6O2,  with  its  two  carbon 
atoms,  to  stearic  acid,  C18H36O2,  with  its  eighteen, 
they  all  have  exactly  two  oxygen  atoms.  These 
are  the  only  oxygen  atoms  in  the  fat  molecule. 
Each  fatty  acid  molecule  has,  of  course  (like  all 
acids),  one  hydrogen  atom,  which  is  replaceable 
when  the  acid  combines  with  a  base. 

The  other  component  of  fats  is  glycerin.    Glycerin 


82  CHEMISTRY   FOR   NURSES 

(Chapter  VIII)  is  an  alcohol  and  has  three  OH  groups. 

Its  formula  is  :  — 

CH2OH 

I 
CHOH 

I 
CH2OH 

Now,  alcohols  act  like  bases ;  that  is  to  say,  they 
combine  with  and  neutralize  acids.  (For  instance, 
the  reader  will  remember  that  when  sodium  hydrate, 
NaOH,  is  neutralized  by  hydrochloric  acid,  HCl, 
the  sodium  atom  separates  from  the  OH  group  and 
joins  the  acid,  displacing,  of  course,  the  H  from  the 
acid  molecule.  The  same  thing  happens  when  glyc- 
erin and  fatty  acids  combine  and  neutralize  each 
other.)  The  OH  groups  separate  from  the  glycerin 
to  be  replaced  by  fatty  acid  molecules.  And  as 
there  are  three  OH  groups  to  the  glycerin  molecule, 
each  one  of  them  in  turn  can  be  replaced  by  a  fatty 
acid :  all  three  of  the  OH  group  may  be  replaced 
by  the  same  fatty  acid  or  they  may  be  replaced  by 
different  fatty  acids.  Thus  one  might  get  a  fat  whose 
structure  would  look  like  this :  — 

CH2  —  Stearic  acid 

,  I 

CH  —  Stearic  acid 

I 

CHg  —  Stearic  acid 


FATS  83 

or  one  whose  structure  would  look  like  this : — 
CH2  —  Stearic  acid 

I 

CH  —  Palmitic  acid 

I 

CH2  —  Butyric  acid 

As  there  are  a  great  many  different  fatty  acids  to 
choose  from,  there  is  a  possibility  of  a  great  many 
different  fats. 

The  fats  of  no  two  animals  or  plants  are  the  same 
in  composition.  The  different  flavors  of  various 
kinds  are  due  to  the  different  fatty  acids.  Like- 
wise the  exact  temperature  at  which  each  fat  melts 
or  solidifies  is  constant  and  characteristic.  For  all 
fats  can  be  obtained  solid  or  fluid,  according  to  the 
temperature.  Those  which  are  fluid  at  ordinary 
room  temperatures  (olive  oil,  for  example)  can  be 
solidified  at  lower  temperatures. 

PHYSICAL   PECULIARITIES   OF   FATS 

A  little  knowledge  of  some  of  the  physical  peculiar- 
ities of  fats  illuminates  a  number  of  common  domestic 
phenomena.  Fat  readily  soaks  into  many  sub- 
stances and  changes  their  light-transmitting  property 
so  as  to  cause  grease  spots.  A  drop  of  fat  on  a  piece 
of  paper  makes  a  spot  which  is  translucent  when 


84  CHEMISTRY   FOR   NURSES 

held  to  the  light.  This  effect  on  paper  offers  a  con- 
venient test  to  determine  whether  any  substance  con- 
tains fat. 

Solubility.  —  Fat  is  not  soluble  in  water,  but  is 
somewhat  soluble  in  alcohol  and  extremely  soluble 
in  ether.  Test  this  by  pouring  a  drop  or  two  of  olive 
oil  into  tubes  of  water,  alcohol,  and  ether,  and  shaking 
well.  On  standing,  all  the  oil  quickly  collects  in 
droplets  at  the  top  of  the  water ;  some  of  it  is  dis- 
solved in  the  alcohol,  and  all  of  it  disappears  in  the 
ether.^  Ether  and  such  commercial  products  as 
naphtha,  benzine,  and  gasoline  owe  their  cleansing 
power  entirely  to  their  ability  to  dissolve  fats. 

Emulsions.  —  When  fat  is  mixed  in  certain  kinds 
of  fluids  it  neither  dissolves  nor  collects  again  as 
large  globules.  Instead  it  divides  automatically  into 
smaller  and  smaller  globules,  until  the  droplets  be- 
come microscopic  in  size  and  remain  uniformly 
suspended  throughout  the  fluid.  Such  mixtures  are 
opaque  and  are  called  emulsions.  Milk  is  a  good 
example  of  an  emulsion. 

In  order  that  an  emulsion  can  be  formed,  there 
must  be  some  substance  in  the  solution  which  forms 

^  Remember  the  inflammable  nature  of  ether  and  do  not 
perform  this  experiment  if  there  is  an  open  flame  in  the  same 
room. 


FATS  85 

a  film  on  the  surface  of  the  globules  of  fat  and 
prevents  their  running  together.  In  milk  this 
function  of  preventing  the  fat  globules  from  run- 
ning together  is  performed  by  proteids.  In  other 
instances  soap  performs  this  function.  Dissolve  a 
little  green  soap  in  water  and  shake  with  it  a  few 
drops  of  olive  oil.  Instead  of  collecting  at  the  top, 
the  oil  remains  suspended  in  the  solution  as  a  milky 
emulsion. 

SOAPS 

Ever  since  the  time  of  the  ancient  Romans,  perhaps 
even  longer,  housewives  have  manufactured  crude 
soap  for  cleansing  purposes  by  boiling  together  fat 
and  lye  (an  alkaline  substance  dissolved  from  the 
ashes  of  plants).  This  traditional  process  was 
handed  down  from  generation  to  generation,  but  it 
was  not  until  the  beginning  of  the  nineteenth  cen- 
tury that  the  underlying  chemistry  was  discovered, 
so  that  purified  soap  could  be  made.  And  only  in 
relatively  recent  years  has  it  been  detected  that  soap 
is  formed  in  the  intestines  and  plays  an  important 
role  iQ  the  digestion  of  fats. 

Manufacture  of  Soap.  —  Let  us  manufacture 
some  soap  ourselves.  Then  we  wUl  be  able  to  un- 
derstand its  chemical  composition.    Soap  is  made  by 


86  CHEMISTRY   FOR   NURSES 

heating  fat  with  strong  alkali.  Add  some  olive  oil  ^ 
to  a  30  %  solution  of  sodium  hydrate  in  alcohol  and 
boil  gently  in  a  water  bath.  The  oil  gradually 
disappears  in  the  solution  which  remains  clear,  and 
the  result  is  an  alcoholic  solution  of  soap  (like 
tincture  of  green  soap) .  Several  tests  can  be  appHed 
to  show  that  this  is  soap  and  not  merely  dissolved 
fat.  Thus  a  little  of  it  poured  into  water  forms 
a  smoky  solution  which  on  shaking  lathers.  No 
oil  globules  are  seen  in  the  water. 

The  alkali  is  used  up  in  this  process  of  making 
soap.  If  we  were  to  keep  on  adding  olive  oil  until 
no  more  would  disappear  in  the  solution,  we  would 
find  that  the  sodium  hydrate  had  been  almost  com- 
pletely neutralized. 

Now  what  neutralized  the  alkali?  Evidently 
the  fatty  acids  present  in  the  fats.  So  what  the 
sodium  hydrate  actually  did  was  to  split  the  fat  into 
its  constituent  fatty  acids  and  glycerin,  and  then  to 
neutralize  the  fatty  acids. ^  So  soaps  are  compounds 
(really  salts,  see  Chapter  VII)  of  sodium  or  potassium 
with  fatty  acids,  just  as  fats  are  compounds  of  glycerin 

^  One  of  the  finest  kinds  of  soap,  Castile  soap,  is  made  from 
olive  oil,  and  has  been  so  made  for  centuries. 

2  Glycerin,  of  course,  is  set  free  in  this  exchange,  and  this  is 
the  regular  process  of  manufacturing  glycerin ;  it  is  a  by-product 
of  soap  making. 


FATS  >    87 

toith  fatty  acids.  Thus  our  ordinary  hard  soap  con- 
sists of  sodium  salts,  and  soft  soap  of  potassium, 
salts  of  fatty  acids. 

Solubility  of  Soaps.  —  Soaps  have  very  character- 
istic properties,  a  knowledge  of  which  is  of  some 
practical  interest.  Sodium  and  potassium  soaps 
are  soluble  in  water  and  form  rather  smoky-looking 
solutions  which  on  shaking  give  a  typical  foamy 
lather.  They  are  soluble  in  alcohol  (for  instance, 
tincture  of  green  soap),  butj  unlike  fats,  not  in  ether} 

Why  Salt  Water  is  not  good  for  Washing.  — 
Soap,  however,  is  not  soluble  in  salt  water ;  in  fact, 
salt  precipitates  it.  This  can  be  demonstrated  by 
dissolving  some  tincture  of  green  soap  in  water  and 
adding  to  it  some  strong  salt  water  (made  by  dis- 
solving a  few  grams  of  table  salt  in  a  test  tube  of 
water).  A  dense  white  precipitate  is  formed  at 
once.  This  process  is  known  as  '^  salting  out  "  and 
is  used  in  manufacturing  in  order  to  free  soap  of 
impurities.  The  same  ''  salting  out  '^  is  what  pre- 
vents us  from  washing  our  hair  with  soap  in  the 

^  This  is  the  reason  that  in  "  scrubbing  up  "  the  skin  for 
operations  with  soap,  alcohol,  and  ether,  the  three  ought  always 
be  used  in  the  order  named.  The  alcohol  removes  any  soap 
not  washed  away  by  water.  The  ether  removes  the  alcohol 
and  any  trace  of  grease  not  removed  by  the  soap.  What  ether 
is  left  on  the  skin  disappears  by  evaporation. 


88  CHEMISTRY  FOR  NURSES 

ocean.  The  greasy  lumps  which  form  in  the  hair 
are  precipitated  soap. 

^^  Hard  ^^  Water.  —  Not  every  soap  is  soluble  in 
water;  calcium  soap,  formed  by  the  union  of  the 
metal  calcium  with  fatty  acids,  is  insoluble.  More- 
over, calcium  has  a  great  aflSnity  for  fatty  acids,  so 
that  whenever  calcium  in  solution  comes  into  con- 
tact either  with  fatty  acid  or  with  ordinary  soap 
the  insoluble  calcium  soaps  are  formed  at  once. 
Thus  pour  some  limewater  into  soap  water.  A 
curdy  white  precipitate  is  formed  at  once.  The 
reason  that  so-called  ''  hard  water  "  which  occurs  in 
certain  parts  of  the  country  is  not  suitable  for  wash- 
ing purposes  is  that  it  contains  small  amounts  of 
calcium  salts  dissolved  from  rocks  in  the  ground.^ 

How  Soap  Cleanses.  —  Soaps  emulsify  fats.  The 
cleansing  property  of  soap  is  largely  due  to  this  power 
of  emulsifying  the  fat  and  grease  which  collect  on 
the  surface  of  the  skin  and  of  the  objects  we  handle ; 
by  emulsifying  this  film  of  fat  the  soap  removes  with 
it  the  particles  of  dust  and  the  germs  that  are  stick- 
ing in  the  fat.^ 

1  See  Mclsaacs,  "Hygiene  for  Nurses." 

2  The  greasy  scum  left  in  the  bathtub  is  due  to  the  fact  that 
the  large  amount  of  water  dilutes  the  soap  until  it  is  no  longer 
able  to  hold  all  the  fat  in  emulsion. 


FATS  89 

The  important  points  to  remember  in  this  chapter 
are  that  neutral  fats  are  compounds  of  fatty  acids 
and  inorganic  bases,  that  alkaHes  make  soaps  from 
fats,  and  that  soaps  in  turn  emulsify  fats.  Under- 
standing this  will  help  greatly  to  understand  the 
splitting  apart  of  fats  that  occurs  in  the  process  of 
digestion  to  be  discussed  in  a  later  chapter. 


CHAPTER  XI 

Proteids 

As  the  chemists  made  one  successful  attack  after 
another  on  various  kinds  of  organic  substances,  as 
they  unraveled  the  complicated  structures  of  car- 
bohydrates, of  alkaloids,  as  they  made  syntheti- 
cally all  sorts  of  compounds  from  indigo  to  rubber, 
there  always  remained  one  class  of  substances  that 
contained  nitrogen  and  that  defied  their  keenest 
efforts.  And  strangely  enough  these  substances 
seemed  to  be  the  most  important  of  all.  They  were 
found  in  every  living  cell;  they  turned  out  to  be  ab- 
solutely indispensable  in  the  food  of  every  animal.  In 
fact,  so  fundamental  were  these  substances  that  they 
were  often  referred  to  as  living  matter  par  excellence, 
as  the  physical  basis  of  life.  And  yet  until  a  few 
years  ago  we  had  no  conception  of  their  chemical 
structure  at  all. 

To-day  this  is  changed.  The  proteids  are  still 
far  from  an  open  book.  The  exact  structures  of 
only  a  few  of  the  simplest  ones  are  known.    Their 

90 


PROTEIDS  91 

'  synthesis  has  been  little  more  than  begun.  Yet  the 
general  plan  of  the  proteid  molecule  is  no  longer  a 
mystery. 

Elementary  Composition.  —  It  is  true  that  the 
early  chemists,  from  the  time  of  Liebig  and  Wohler 
on,  knew  the  elements  of  which  proteids  were  com- 
pounded, —  carhoUj  hydrogen,  oxygen^  and  nitrogen 
(and  sometimes  in  addition  sulphur,  phosphorus, 
and  iron).  They  were  even  able  to  find  out  with 
considerable  accuracy  how  much  of  each  of  these 
elements  was  present  in  a  given  proteid.  But  there 
they  had  to  stop.  The  proteid  molecule  was  of  such 
enormous  size  (containing  not  merely  dozens  but 
hundreds  and  sometimes  even  thousands  of  atoms) 
and  of  so  great  complexity  that  analysis  seemed 
impossible. 

Structure.  —  The  solution  of  the  mystery  has 
come  from  a  careful  study  of  the  products  of  the 
digestion  of  proteids,  and  from  imitation  of  this 
digestion  by  the  sphtting  up  of  the  proteid  molecule 
with  strong  acids.  By  these  methods  it  was  found 
that  the  proteid  molecules  are  vast  congeries  of  linked- 
together  amino  acids. 

What  are  amino  acids?  They  turn  out  to  be 
our  old  friends  the  fatty  acids,  into  the  molecule  of 
each  of  which  a  new  nitrogen-containing  atom  group, 


92  CHEMISTRY   FOR   NURSES 

NH2  (known  as  amine  and  resembling  in  some 
ways  ammonia,  NH3),  has  been  inserted. 

Not  that  proteids  are  composed  exclusively  of 
these.  There  are  other  atom  groups,  such  as,  for 
instance,  aromatic  groups  (the  closed  rings  of  carbon 
atoms  referred  to  in  the  Chapter  on  Organic  Chemistry ; 
see  page  62). 

Classes  of  Proteids.  —  But  before  we  get  too 
deeply  involved  in  their  chemical  structure  let  us 
get  acquainted  a  little  more  closely  with  some  of  the 
proteids  themselves.  The  number  of  different  pro- 
teids is  almost  unlimited.  Each  animal  or  plant 
possesses  at  least  several  proteids,  and  it  is  likely 
that  no  two  proteids  in  separate  species  of  animals 
or  plants  are  identical.  This  is  readily  understood 
when  we  think  of  the  complexity  of  the  proteid  mole- 
cule and  remember  that  the  shifting  in  position  of  a 
few  atoms  makes  a  new  substance.  We  will  discuss 
three  principal  classes  of  proteids,  the  simple  pro- 
teids, the  compound  proteids,  and  the  albuminoids. 

Simple  Proteids.  —  The  most  important  proteids 
are  the  so-called  native,  or  typical,  or  simple  ^  pro- 
teids such  as  the  albumins  and  globulins  found  in  egg 

1  The  term  "  simple, "  though  often  used,  is  really  poor  be- 
cause these  are  actually  among  the  most  complex  oi  all  pro- 
teids and  have  molecules  of  very  great  size. 


PROTEIDS  93 

white,  in  blood  serum  and  in  milk  whey,  the  gluten 
and  legumen  of  plants,  the  myosin  or  muscle  proteid, 
and  the  fibrinogen  of  blood  plasma  (from  which  is 
derived  the  fibrin,  —  the  tough  part  of  a  blood  clot). 

Compound  Proteids.  —  Of  equal  rank  with  these 
are  the  compound  proteids  from  the  molecules  of 
which  some  special  non-proteid  group  can  be  split 
off.  Thus  hcemoglohin,  the  important  red  coloring 
matter  of  the  blood  cells,  is  composed  of  an  iron- 
containing  fraction  combined  with  proteid;  the 
caseinogen  of  milk  (from  which,  on  coagulation, 
comes  the  casein,  curd,  cheese)  is  a  compound  of 
phosphoric  acid  and  proteid ;  mucin,  found  in  mucus, 
is  a  compound  of  sugar  with  proteid. 

Albuminoids.  —  All  the  above  proteids  are  very  soluble 
and  when  taken  as  food  are  easily  digested  and  as- 
similated. There  are  other  proteids  (called  albu- 
minoids) which  form  the  connective  and  protecting 
tissues  of  the  body ;  they  are  more  or  less  insoluble 
and  are  of  relatively  little  value  in  nutrition.  Among 
these  are  collagen  (the  basis  of  connective  tissue 
and  tendons,  from  which  by  prolonged  boiling  we 
obtain  gelatin),  and  keratin,  the  proteid  of  skin, 
hair,  and  nails.  Keratin  contains  much  sulphur, 
and  it  is  the  oxidized  sulphur  which  gives  the  dis- 
gusting smell  to  burnt  hair  or  skin. 


94  CHEMISTRY   FOR  NURSES 

Now  that  we  have  an  idea  of  what  the  proteids  are 
and  where  they  are  to  be  found,  let  us  consider  some 
of  their  properties. 

SOLUBILITY 

Proteids  (except  the  albuminoids)  are  very  soluble 
in  salt  water  and  also  (except  the  globulins)  in  plain 
water.  Their  solutions  are  opalescent  and  are  very 
viscid  and  sticky,  so  that  even  very  dilute  solutions 
(as  dilute  as  one  part  of  proteid  in  one  thousand  of 
water)  will  form  a  more  or  less  permanent /oam  when 
shaken.  As  found  in  living  cells  proteids  are  always 
dissolved  or,  at  least,  combined  with  much  water. 

COAGULATION 

Every  one  knows  the  change  in  appearan  ce  of  meat  or 
eggs  after  cooking.  This  hardening  is  an  instance  of  an 
alteration  produced  by  heat  in  almost  all  proteids,^  and 
known  as  coagulation.  Superficially  it  has  a  certain 
resemblance  to  precipitation  of  a  solid  from  a  solu- 
tion. But  coagulation  differs  from  precipitation  in 
this  regard :  it  is  not  reversible,  it  is  permanent;  a 
proteid  once  coagulated  is  unalterably  changed; 
nothing  can  restore  it  to  its  former  state.    And 

*  Gelatin,  certain  vegetable  proteids,  and  the  partly  digested 
proteids  (proteose  and  peptone  mentioned  below)  are  exceptions. 


PROTEIDS  95 

living  cells  whose  proteids  are  coagulated  are  inevi- 
tably killed. 

This  is  the  reason  for  the  sterilizing  effect  of  heat 
The  remarkable  resistance  of  the  spores  of  certain 
bacteria  to  heat  sterilization  ^  will  at  once  occur  to 
the  reader.  Can  this  be  explained?  If  all  living 
cells  contain  proteids,  why  are  not  the  proteids  of 
the  spores  coagulated  by  steam  and  the  spores  at 
once  killed  ?  Proteids  as  they  ordinarily  occur  con- 
tain water;  but  when  thoroughly  dried  they  are 
coagulated  only  by  extreme  degrees  of  heat.  In 
spores  the  proteids  are  condensed  so  as  to  be  almost 
free  of  water.  The  resistance  of  dried  proteid  to 
coagulation  explains  also  the  well-known  superiority 
of  moist  heat  (steam)  to  equal  degrees  of  dry  heat  in 
sterilization. 

Coagulation  Test  for  Albumen.  —  Heat  coagu- 
lation affords  a  very  delicate  way  of  testing  for  any 
coagulable  proteid,  even  in  small  traces.  Thus  if 
a  drop  of  blood  serum  is  mixed  in  a  test  tube  of  water 
and  the  test  tube,  held  by  the  bottom,  is  brought  to 
a  flame  so  that  the  upper  layer  of  fluid  boils,  a  cloud 
forms  in  the  upper  part.  On  addition  of  a  drop  of 
dilute  acid  the  cloud  becomes  much  denser,  because 
a  slightly  acid  reaction  aids  in  the  coagulation  of 
^See  Mclsaacs,  "Bacteriology  for  Nurses." 


96  CHEMISTRY   FOR  NURSES 

proteids.  This  method  is  used  to  detect  traces  of 
albumin  in  urine. 

Coagulating  Effect  of  Salts  of  the  Heavy  Metals.  — 

Coagulation  can  be  brought  about  not  only  by  heat, 
but  by  many  chemical  agencies}  Thus  if  to  a  test 
tube  containing  egg  white  or  blood  serum  is  added 
a  solution  of  bichloride  of  mercury  or  of  silver  nitrate, 
a  dense  coagulum  is  precipitated  at  once.  These 
and  many  similar  substances  owe  their  disinfecting 
power  as  well  as  their  local  poisonous  properties  to 
their  coagulating  effect  on  proteids.^  Their  mode  of 
action,  however,  betrays  their  limitations  as  disin- 
fectants, because  in  coagulating  proteid  they  com- 
bine with  it  and  hence  are  unable  to  penetrate  deeply 
or  to  disinfect  matter  containing  much  proteid. 

TESTS  FOR  PROTEID 

There  are  many  useful  tests.  The  coagulation 
test  is  often  applied.    For  proteids  in  general  the 

1  The  term  *'  coagulation"  is  also  unfortunately  applied  to  the 
clotting  of  blood  and  milk.  These  processes  are  different  from 
ordinary  coagulation  and  are  really  due  to  the  formation  of 
special  new  proteids,  —  fibrin  from  the  fluid  fibrinogen  of 
plasma,  casein  from  the  fluid  caseinogen  of  milk. 

2  By  no  means  all  the  things  which  precipitate  proteids  coagu- 
late them.  Thus  alcohol  (if  apphed  for  a  short  time),  or  con- 
centrated salt  solutions,  precipitate  without  coagulating.  Such 
precipitated  proteids  can  be  redissolved. 


PROTEIDS  97 

nitric  acid  test  is  very  convenient.  Probably  the 
reader  has  already,  in  handling  nitric  acid,  uncon- 
sciously applied  this  test  to  the  skin  of  fingers. 
Nitric  acid,  though  colorless,  stains  the  skin  a  deep 
yellow.  If  the  very  natural  attempt  is  made  to  neu- 
tralize the  acid  by  applying  some  alkali,  such  as  am- 
monia, the  stain  instead  of  disappearing  becomes 
of  an  intense  orange  color.  (Add  a  little  strong 
nitric  acid  to  some  egg  albumin.  The  acid  first 
precipitates  the  albumin,  then  dissolves  it,  and  turns 
it  yellow.  On  addition  of  an  excess  of  ammonia 
the  color  deepens  and  becomes  a  beautiful  orange.) 

THE  FUNCTIONS  OF  PROTEIDS 

It  has  already  been  stated  that  proteids  are  indis- 
pensable in  the  diet  of  animals.  The  amount  of 
proteid  actually  needed  may  be  exceedingly  small, 
but  sooner  or  later  every  animal  must  receive  jproteids 
to  replace  the  burnt-up  or  destroyed  proteids  in  its 
own  tissues,  —  otherwise  it  will  die.  An  animal 
can  do  without  fats  provided  it  gets  enough  carbo- 
hydrates to  supply  it  with  energy,  or  without  carbo- 
hydrates provided  it  gets  enough  fats.  But  it  is 
constantly  using  up  its  own  proteid  in  bringing  about 
the  various  chemical  processes  of  life  and  the  used- 
up  proteid  must  be  replaced. 


98  CHEMISTRY   FOR   NURSES 

Where    do    Animals   get   their   Proteid  ?  —  The 

proteids  in  animals  are  all  ultimately  derived  from 
plants.  In  the  case  of  the  herbivorous  or  plant- 
eating  animals,  the  proteids  are  derived  directly  by 
the  process  of  digestion  from  plants.  The  carnivo- 
rous or  flesh-eating  animals  get  their  proteids  second- 
hand, so  to  speak,  from  the  flesh  of  the  plant-eating 
animals.  The  plants  in  turn  manufacture  their 
proteid  from  inorganic  nitrogen  compounds  (am- 
monia, nitrites,  and  nitrates)  in  the  soil.  An  animal 
could  die  of  '^  nitrogen  starvation "  in  spite  of 
breathing  the  pure  nitrogen  which  forms  70%  of  the 
air,^  if  it  were  not  supplied  with  proteid  directly 
or  indirectly  by  plants. 

Why  are  proteids  so  indispensable?  We  do  not 
know  enough  about  the  chemistry  of  the  cell  as  yet 
to  give  a  complete  answer  to  this  question.  For 
some  reason  the  cell  must  constantly  destroy  its  own 
proteid  in  order  to  maintain  life.  The  proteids 
have  been  compared  to  the  kindlings  of  a  fire,  of 
which  carbohydrates  and  fats  are  the  staple  fuel. 

^  Plants  also  are  unable  to  utilize  the  nitrogen  of  the  air. 
The  only  way  in  nature,  so  far  as  we  know,  by  which  the  inert 
nitrogen  of  the  air  is  converted  into  the  forms  in  which  plants 
can  utihze  it,  is  by  the  action  of  certain  bacteria  which  grow 
in  the  soil.  So  ultimately  all  other  animal  and  vegetable  Ufe  is 
dependent  on  these  nitrifying  bacteria  of  the  soil. 


PROTEIDS  99 

Not  every  nitrogen-containing  substance  in  the 
body  or  in  the  food  is  proteid.  There  are  many 
other  nitrogenous  compounds,  —  mostly  derived 
from  proteids.  Meat  extradj  for  instance,  —  bouillon, 
beef  tea,  —  consists  of  such  nitrogenous  but  non- 
proteid  substances  which  although  practically  devoid 
of  nutrition  are  nevertheless  of  great  value  in  diet 
because  of  their  flavor  and  their  stimulating  effect 
on  digestion. 

PARTLY    DIGESTED    PROTEIDS    (PROTEOSES  AND    PEP- 
TONES) 

The  proteids  we  have  discussed  thus  far  occur  as 
part  of  the  living  organism.  When,  either  as  the 
result  of  digestion  or  of  the  action  of  strong  acids  or 
alkalies,  the  proteid  molecule  is  broken  up,  the  first 
large  fragments  that  result  are  the  molecules  of  sub- 
stances known  as  proteoses.  When  these  are  a  little 
further  disintegrated  the  result  is  peptones.  Proteose 
molecules  contain  a  large  number  of  amino  acids, 
peptone  molecules  a  smaller  but  still  considerable 
number.  Proteoses  and  peptones  are  still  proteids 
and  give  all  the  proteid  tests.  However,  they  cannot 
he  coagulated.  (This  can  be  demonstrated  by  dis- 
solving in  water  some  powdered  nxeat  peptone,  .de- 
rived from  the  artificial  digei^tioh  of  meat  and  really 


100  CHEMISTRY   FOR  NURSES 

containing  proteoses  as  well  as  peptones.  On  boil- 
ing and  adding  dilute  acetic  acid  to  this,  absolutely 
no  trace  of  coagulation  is  seen.)  When  peptone 
molecules  are  further  broken  up  the  resulting  sub- 
stances are  no  longer  proteids,  but  amino  acids  or 
small  groups  of  amino  acids  called  polypeptids. 

Proteoses  and  peptones  have  not  the  bland  or 
pleasant  taste  of  other  proteids,  but  taste  very  hitter 
(whence  the  bitter  taste  of  peptonized  foods). 


CHAPTER  XII 
Digestion 

Our  bodies  are  built  up  chiefly  of  proteids,  fats, 
carbohydrates,  and  inorganic  substances :  so  is  our 
food.  But  the  particular  proteids,  fats,  carbo- 
hydrates, and  inorganic  substances  in  our  food  are 
entirely  different  from  those  in  our  body.  The 
process  by  which  those  in  our  food  become  chemically 
changed  into  those  in  our  body  is  the  process  of 
digestion.     It  is  purely  a  chemical  process. 

What  brings  about  the  Chemical  Changes  in  the 
Body  ?  —  During  digestion  very  profound  changes 
are  brought  about  in  the  food  materials.  These 
are  brought  about  by  the  action  of  certain  substances 
known  as  enzymeSj  which  are  produced  in  the  mouth, 
stomach,  and  intestines.  The  enzymes  (formerly 
called  ferments  or  unorganized  ferments)  are  very 
wonderful  substances.  Each  enzyme  is  able  to  work 
on  one  particular  kind  of  substance,  —  and  no  other. 
On  this  account  an  enzyme  has  been  compared  to  a 
key  which  will  fit  one  particular  lock,  —  that  is, 
will  unlock  one  particular  kind  of  molecule.    En- 

101 


102  CHEMISTRY   FOR  NURSES 

zymes  do  the  work  which  otherwise  can  only  be  done 
by  very  powerful  chemical  processes,  such  as  strong 
acids  or  alkalies,  considerable  heat,  and  similar 
means.  Yet  enzymes  themselves  are  present,  even 
when  they  produce  great  effects,  only  in  small  traces 
and  they  are  almost  inert  and  inactive  chemically 
against  anything  excepting  the  particular  kind  of 
substance  that  they  can  digest.  Thus,  to  carry 
the  illustration  a  little  farther:  if  enzymes  corre- 
spond to  keys  which  will  unlock  only  particular  doors, 
the  ordinary  chemical  process  might  be  compared 
to  battering  rams  which  will  break  through  any  door. 

Chemical  Nature  of  Enzymes.  —  The  exact  chemi- 
cal composition  of  enzymes  is  not  known,  but  they 
are  almost  certainly  proteid.  All  of  them  can  he 
destroyed  or  killed  hy  boiling,  and  in  general  by  all 
of  the  same  things  as  coagulate  proteids.  Each  enzyme 
has  certain  particular  set  conditions  which  it  must 
have  in  order  to  work.  Thus  most  of  our  digestive 
enzymes  work  best  at  body  temperature.  Some 
enzymes  will  work  only  if  in  slightly  alkaline  solu- 
tion ;  others  only  if  the  solution  is  acid ;  some  can 
work  in  either  acid  or  alkaline  solution. 

All  Cells  contain  Enzymes.  —  We  will  discuss 
only  the  most  important  enzymes  that  are  found 
in  the  human  digestive  tract,  but  the  student  ought 


DIGESTION  103 

to  know  that  there  are  really  very  many  more 
enzymes  than  these.  Every  living  cell  contains 
enzymes  and,  in  fact,  brings  about  most  of  the  chemi- 
cal changes  which  are  necessary  for  its  life,  by  means 
of  enzymes.  Furthermore,  the  action^of  enzymes  is 
not  only  to  break  dovm  substances  into  simpler  forms, 
as  occurs  in  our  digestive  tract,  l:)ut  also  to  build  up 
simpler  substances  into  the  more  complicated  ones 
needed  by  the  body. 

SALIVA 

The  saliva  is  the  first  digestive  juice  which  the 
food  meets.  It  contains  one  important  enzjTne,  — 
ptyalin  or  amylase.  (The  new  system  of  naming 
enzymes  uses  the  ending  "  ase  "  to  a  word  to  in- 
dicate enzyme,  and  attaches  the  ending  to  the  name 
of  the  substance  that  the  enzyme  works  on :  thus, 
amylum  (starch),  amylase.)  Ptyalin  breaks  starch 
dovm  to  dextrin,  then  to  maltose,  and  then,  finally, 
to  glucose,  or  simple  sugar.^ 

In  the  Chapter  on  Carbohydrates  it  was  stated 
that  boiHng  with  a  strong  acid  would  reduce  starch 
to  dextrose.     Saliva  will  do  the  same  thing  and  more 

^  The  action  of  diastase  or  malt  extract  (the  vegetable  en- 
zyme of  germinating  barley)  on  starch  is  closely  similar,  but 
does  not  proceed  quite  so  far. 


104  CHEMISTRY   FOR   NURSES 

quickly,  and  without  boiling.  This  can  be  proved 
by  a  very  simple  experiment.  Take  a  test  tube 
full  of  saliva  obtained  simply  by  chewing  on  a  piece 
of  paper.  Filter  the  saliva  to  make  it  clear.  Take 
a  test  tube  of  starch  paste  and  first  apply  to  the 
starch  two  tests  to  prove  that  it  is  starch  and  is 
free  from  any  simple  sugar.  The  addition  of  a  drop 
of  iodine  turns  it  a  deep  blackish  blue.  Boiling  a 
drop  or  two  of  the  starch  paste  with  Fehling^s  solu- 
tion gives  no  reduction  of  copper  (no  yellow  precipi- 
tate). Now  mix  some  saliva  and  starch  paste  in  a 
test  tube  and  put  the  test  tube  in  a  water  bath  at 
body  temperature  for  only  a  few  minutes.  Then 
test  the  contents  of  the  test  tube  again  with  iodine, 
and  you  will  see  instead  of  the  deep  blue  color  a 
brownish  color  indicating  that  there  is  dextrin  pres- 
ent. Add  a  few  drops  to  Fehling^s  solution  and  boilj 
and  you  see  an  abundant  yellow  precipitate,  —  an  in- 
dication that  some  of  the  starch  has  been  broken  down 
beyond  the  dextrin  stage  to  dextrose  (grape  sugar) 
by  the  action  of  ptyalin. 

What  Effect  has  Boiling  on  Enzymes  ?  — Now 
repeat  the  experiment ;  only  instead  of  using  the 
fresh  saliva  use  some  saliva  whichis  first  boiled  and  you 
will  see  that  nothing  happens.  The  starch  remains 
quite  unchanged.    The  boiling  kills  the  enzymes. 


DIGESTION  105 

Effect  of  Acids  on  Starch  Digestion.  —  Saliva,  as 
one  can  see  by  the  bluish  color  which  it  gives  to  lit- 
mus paper,  is  weakly  alkaline  in  reaction.  Ptyalin 
works  best  in  an  alkaline  or  neutral  fluid.  An  acid 
reaction  not  only  stops  its  action,  hut  quickly  destroys 
it.  If  one  adds  a  little  hydrochloric  acid  to  saliva, 
lets  it  stand  a  few  minutes,  and  again  tests  its  effect 
on  starch,  one  can  see  that  it  has  absolutely  no  diges- 
tive power.  The  acid  kills  the  enzyme  quite  as 
effectually  as  boiling  does. 

GASTRIC   DIGESTION 

The  next  digestive  secretion  is  the  gastric  juice. 
It  is  strongly  acid  in  reaction  due  to  the  presence  of 
hydrochloric  acid  in  the  strength  of  about  0.2%. 
Gastric  juice  contains  two  important  enzymes, — rennin 
and  pepsin.  Rennin  has  the  power  of  coagulating 
the  caseinogen  of  milk.  The  coagulation  of  milk  is 
the  preliminary  stage  to  its  digestion.  Artificial 
gastric  juice,  prepared  by  making  an  extract  of  the 
stomach  of  the  pig,  is  sold  commercially  as  pepsin 
and  is  used  medicinally.  This  pepsin  dissolved  in 
water  and  added  to  milk,  which  is  then  allowed  to 
stand  at  body  temperature  for  a  few  minutes, 
promptly  curdles  the  milk. 


106  CHEMISTRY   FOR  NURSES 

Rennin.  —  Rennin  is  very  difficult  to  separate 
from  pepsin.  That  is  the  reason  that  we  use  the 
substance  called  pepsin,  which  is  really  not  pure 
pepsin,  but  an  extract  of  stomach  glands  containing 
both  pepsin  and  rennin,  for  coagulating  milk.  After 
the  milk  has  coagulated,  the  fluid  part  which  sepa- 
rates out  is  whey.  If  whey  is  heated  at  once,  the 
pepsin  does  not  have  time  to  produce  much  peptone 
or  proteose.  But  if  it  is  allowed  to  stand,  the  pro- 
teoses and  peptones  which  form  give  it  a  bitter  taste. 
The  fat  in  the  milk  for  the  most  part  remains  tangled 
in  the  mesh  of  the  coagulated  casein.  Rennin 
works  either  in  an  acid  or  a  neutral  medium. 

Pepsin.  —  Pepsin  is  the  stomach  enzyme  which 
digests  proteids.  It  dissolves  them  and  breaks 
them  down  partly  or  entirely  to  proteoses  and  pep- 
tones. It  is  active  only  in  the  presence  of  acid  and 
it  is  destroyed  if  the  reaction  becomes  alkaline. 

The  effect  of  pepsin  on  little  pieces  of  coagulated 
egg  white  and  on  little  shreds  of  washed  blood  fibrin 
can  easily  be  studied .  Prepare  the  fibrin  first  by  wash- 
ing a  piece  of  blood  clot  obtained  at  the  slaughter- 
house in  running  water  until  all  the  red  blood  cells 
are  washed  out.  From  the  yellow  fibrous  clot  that 
is  left  tear  off  five  little  shreds  and  put  them  in  test 
tubes.    In  other  test  tubes  put  five  little  cubes  of 


DIGESTION  107 

boiled  egg  white.  Prepare  the  pepsin  solution  by 
dissolving  a  few  grains  of  powdered  or  scaled  com- 
mercial pepsin  in  a  few  cubic  centimeters  of  0.2% 
h3^drochloric  acid.  Add  some  of  this  to  a  tube  con- 
taining fibrin,  and  some  to  a  tube  containing  egg 
white.  Boil  a  little  of  the  pepsin  solution  and  add 
it  to  a  second  pair  of  tubes  with  egg  white  and  fibrin. 
Neutralize  another  portion  with  sodium  hydrate 
and  add  it  to  a  third  pair  of  tubes  of  egg  white  and 
fibrin.  To  a  fourth  set  of  tubes  add  some  strong 
alcohol  and  then  the  pepsin  solution.  In  a  fifth 
pair  of  fibrin  and  egg  white  tubes  put  hydrochloric 
acid  without  pepsin.  Put  all  the  tubes  in  a  water 
bath  at  body  temperature  for  an  hour.  At  the 
end  of  that  time,  in  the  tube  containing  pepsin  and 
hydrochloric  acid  alone,  the  egg  white  and  the  fibrin 
will  have  become  digested,  whereas  in  the  tubes 
containing  boiled  pepsin,  alkaline  pepsin  solution, 
alcohol  with  pepsin,  and  hydrochloric  acid  alone, 
digestion  will  not  have  occurred,  —  the  egg  white 
and  fibrin  will  still  be  there.  In  the  two  tubes,  the 
contents  of  which  are  undergoing  digestion,  at  the 
end  of  fifteen  or  twenty  minutes  both  the  egg  white 
and  the  fibrin  will  look  rather  swollen  and  semi- 
transparent  and  be  apparently  fading  away  at  the 
edges.    At  the  end  of  three  quarters  of  an  hour  the 


108  CHEMISTRY   FOR   NURSES 

fibrin  will  have  almost  entirely  crumbled  away  and 
disappeared.  The  egg  white  too  will  be  almost  en- 
tirely gone,  but  a  little  piece  of  it  may  still  be  left. 
By  boiling  and  filtering  the  fluid  (to  remove  any 
coagulable  proteid)  and  then  with  the  clear  filtrate 
doing  the  nitric  acid  test  for  proteid,  it  is  easy  to 
prove  that  in  this  solution  are  proteoses  and  peptones. 

PANCREATIC   DIGESTION 

When  the  stomach  contents  are  poured  into  the 
intestine  they  meet  at  once  the  pancreatic  juice  and 
bile,  both  of  which  are  alkaline  in  reaction.  The 
alkalinity  at  once  stops  the  further  action  of  the  pep- 
sin, but  not  the  further  digestion  of  proteids,  as  we 
will  see. 

The  pancreatic  juice  is  the  most  important  diges- 
tive secretion  in  the  body,  and  is  emptied  into  the 
duodenum  along  with  the  bile.  It  contains  at  least 
three  very  important  enzymes. 

The  first  of  these  is  amylase,  a  starch-digesting 
enzyme  which  seems  to  be  identical  in  action  with 
ptyalin.  Its  effect  on  starch  is  exactly  the  same  as 
that  of  saliva. 

Trypsin.  How  it  differs  from  Pepsin.  —  The 
second  important  enzyme  is  a  proteid-digesting 
enzyme  known  as  trypsin.    It   attacks  the  same 


DIGESTION  109 

proteids  as  does  pepsin,  but  it  only  acts  in  an  alka- 
line medium  and  it  digests  the  proteid  much  farther 
than  pepsin  ;  namely,  it  not  only  reduces  the  typical 
proteids  to  the  stage  of  proteoses  and  peptones,  but, 
also,  if  the  digestion  is  continued  long  enough,  to  the 
much  simpler  stage  of  polypeptids  and  even  amino 
acids.  It  is  easy  to  demonstrate  the  effects  of  tryp- 
sin by  dissolving  some  commercial  pancreatin  in 
a  weak  alkaline  solution,  namely,  0.4%  sodium 
carbonate  solution,  and  adding  some  of  this  solu- 
tion to  little  pieces  of  fibrin  and  egg  white.  When 
these  stand  for  three  quarters  of  an  hour  at  body  tem- 
perature the  effect  on  the  particles  of  proteid  is  very 
similar  to  the  effect  of  pepsin  in  hydrochloric  acid. 

What  digests  Fats?  —  The  third  important  di- 
gestive enzyme  in  the  pancreatic  juice  is  a  fat-di- 
gesting enzyme  known  as  lipase.  This  has  the  power 
of  splitting  up  fats  into  their  constituent  fatty  acids 
and  glycerin.  In  the  Chapter  on  Fats  I  showed  that 
fats  can  be  split  up  by  boiling  with  powerful  acids 
or  alkahes.  The  feebly  alkaline  pancreatic  juice  does 
exactly  the  same  thing.  This  can  be  conveniently 
demonstrated  by  an  experiment  with  the  fat  of  milk. 

An  Experiment  to  show  the  Splitting  of  Fat  by 
Pancreatic  Lipase.  —  Take  a  large  test  tube  of  milk 
and  to  it  add  a  little  litmus  solution  as  an  indicator 


110  CHEMISTRY   FOR  NURSES 

as  to  whether  the  milk  is  acid  or  alkaHne.  Usually 
the  color  is  pinkish,  indicating  that  the  milk  is 
slightly  acid.  Make  it  slightly  alkaline  by  adding 
a  little  weak  sodium  carbonate  solution.  The  color 
is  now  bluish.  Now  divide  the  milk  in  two  small 
test  tubes :  to  one  test  tube  add  a  little  of  the  arti- 
ficial pancreatic  juice,  made  by  dissolving  pancreatin 
in  sodium  carbonate  solution.  The  color  of  the 
two  tubes  will  still  be  exactly  the  same,  or,  if  it 
is  not,  make  it  so  by  adding  a  little  sodium  carbonate 
solution  to  one  or  the  other.  Now  put  both  tubes 
in  the  water  bath.  After  a  short  while  take  them 
out  and  the  tube  to  which  pancreatic  juice  was 
added  will  now  have  turned  bright  pink.  The 
fatty  acids  of  milk  fat  will  have  been  split  off  from  the 
glycerin  and,  being  acids,  will  have  turned  the  litmus 
solution  red.  This  same  thing  happens  in  the  in- 
testines; but  in  the  intestines  there  is  always  an 
excess  of  alkali  present,  both  from  the  pancreatic 
juice  and  from  the  bile,  so  that  the  fatty  acids  do 
not  turn  the  reaction  actually  acid,  but  are  neutral- 
ized to  form  soaps. 

Of  What  Use  is  Bile  ?  —  The  bile  secreted  by  the 
liver  contains  no  enzymes,  but  is  nevertheless  ex- 
tremely important  for  fat  digestion,  as  it  keeps  the 
contents  of  the  intestines  alkaline  and  thus  aids  in 


DIGESTION  111 

the  emulsification  of  fats,  which  is  essential  to  their 
absorption.  In  neutralizing  the  fatty  acids,  of 
course,  it  forms  soaps  from  them.^ 

INTESTINAL   SECRETION 

Erepsin.  —  The  secretion  of  the  glands  in  the  in- 
testinal wall  also  contains  a  number  of  enzymes. 
There  are  special  enzymes  for  a  number  of  functions : 
for  instance,  enzymes  for  breaking  down  the  di- 
saccharides,  like  cane  sugar  and  milk  sugar,  into 
simple  sugars;  hut  the  most  important  enzyme  con- 
tained in  the  intestinal  juice  is  a  proteid-digesting 
enzyme  known  as  erepsin.  Erepsin  does  not  digest 
the  typical  proteids  at  all,  but  only  attacks  pep- 
tones (which  have  been  produced  by  the  action  of 
pepsin  and  trypsin)  and  breaks  the  peptone  down  to 
amino  acids. 

WHY   DIGESTION   IS   NECESSARY 

Now  let  us  stop  for  a  moment  and  consider  what 
is  the  purpose  of  all  this  chemical  decomposition  of 
food  products  before  absorption.  Our  bodies  are 
built  up  of  carbohydrates,  fats,  and  proteids.  So  is 
our  food.    Why  can  we  not  sjmply  absorb  the  pro- 

1  Absence  of  bile  causes  the  fatty  stools  of  jaundice  patients. 
See  Chapter  XIV,  page  134. 


112  CHEMISTRY   FOR   NURSES 

teid,  fat,  or  carbohydrate  from  the  food  and  use  it 
in  our  bodies?  Each  species  of  animal  has  its  own 
particular  kind  of  proteid,  or  fat,  or  carbohydrate. 
Thus,  though  human  muscle  may  be  built  up 
by  the  eating  of  beef  muscle,  of  chicken  mus- 
cle, of  fish  muscle,  it  is  entirely  different  in  its 
nature  from  any  of  these.  The  muscle  of  the 
Chinaman  who  eats  nothing  but  fish  differs  in  no 
way  from  the  muscle  of  the  Englishman  who 
eats  nothing  but  beef,  and  the  reason  is  now 
perfectly  clear.  The  body  breaks  down  all  the  "pro- 
teid  that  is  offered  to  it,  —  whether  in  the  form  of 
muscle,  grain,  milk,  or  any  other  form,  —  to  the 
simplest  building  stones  of  proteid,  namely,  the 
amino  acids.  It  then  from  the  mixture  selects  those 
particular  amino  acids  which  it  needs  to  build  up  its 
own  kind  of  muscle  proteid  (or  blood  proteid,  or 
other  cell  proteid)  and  rejects  or  burns  up  all  the 
other  amino  acids.  It  does  the  same  thing  to  all 
the  fat  and  carbohydrate  it  gets,  —  disintegrates 
and  then  reconstructs  them  to  suit  its  own  needs. 


CHAPTER  XIII 
Urine 

Functions  of  Kidneys.  —  The  chemistry  of  urine 
is  of  great  practical  importance,  as  the  kidneys  are 
the  chief  excretory  organs.  The  principal  fmiction 
of  the  kidneys  is  to  rid  the  body  of  waste  products 
derived  from  the  hurning  up  of  nitrogenous  compounds. 
Besides  this  the  kidneys  have  to  keep  the  amount  of 
salt  in  the  body  adjusted  to  exactly  the  right  point  by 
excreting  all  superfluous  salt  taken  in  with  the  food, 
and  they  help  the  body  get  rid  of  various  poisonous 
substances  whether  manufactured  by  the  body  itself 
or  absorbed  from  the  intestines  or  elsewhere. 

How  are  Oxidized  Carbon  and  Hydrogen  Ex- 
creted ?  —  In  discussing  the  combustion  of  body  sub- 
stances in  Chapter  IV  it  was  shown  that  the  com- 
bustion of  organic  substances  always  produce  some 
water  and  some  carbon  dioxide.  The  carbon  dioxide 
is  excreted  almost  entirely  by  the  lungs.  Some  of 
the  water  is  excreted  by  the  lungs,  some  by  the  skin, 
and  some  by  the  kidneys. 

I  113 


114  CHEMISTRY   FOR   NURSES 

How  is  Used-up  Nitrogen  Excreted?  —  When 
nitrogenous  substances,  particularly  proteids,  are 
oxidized  in  the  body  the  products  of  combustion  of 
the  nitrogen  are  excreted  chiefly  by  the  kidneys,  in 
the  form  of  several  different  substances.  The  sub- 
stance which  contains  about  three  quarters  of  the 
burnt-up  nitrogen  is  known  as  urea.  By  measuring 
the  amount  of  urea  excreted  in  twenty-four  hours 
doctors  can  get  an  idea  as  to  whether  the  kidneys 
are  able  to  excrete  nitrogenous  waste  sufficiently. 
The  most  important  of  the  other  substances  repre- 
senting the  rest  of  the  burnt-up  nitrogen  is  known 
as  uric  acid;  it  is  believed  to  be  produced  from  the 
oxidation  of  proteids  in  the  nuclei  of  the  body  cells. 
Uric  acid  is  a  normal  constituent  of  urine,  although 
there  is  a  mistaken  popular  impression  that  its 
presence  in  the  urine  means  gout. 

How  Salt  Balance  is  Maintained.  —  Next  to 
nitrogenous  constituents  the  most  important  sub- 
^stances  in  the  urine  are  the  salts.  Practically  all  of 
our  food  contains  more  or  less  salt  and  we  are  thus 
constantly  taking  into  our  bodies  various  amounts  of 
different  kinds  of  salts.  It  is  the  function  of  the 
kidneys  to  maintain  the  proper  concentration  of  the 
proper  salts  in  the  body  by  excreting  all  that  is 
unnecessary. 


UKINB  115 

Purpose  of  Urine  Examination.  —  The  object  of 
urine  examination  is  to  determine  (1)  whether  the 
kidneys  are  performing  their  function  properly, 
(2)  whether  there  is  disease  at  any  point  in  the 
urinary  tract,  (3)  whether  there  is  any  substance 
indicative  of  disease  of  any  other  organ.  There 
are  hundreds  of  different  tests  done  on  urine  for 
special  purposes.  Only  those  will  be  discussed 
which  are  of  great  practical  importance  and  which 
the  nurse  should  know  the  significance  of. 

A  routine  urine  examination  includes  the  follow- 
ing most  important  points :  — 

(1)  Amount  in  twenty-four  hours 

(2)  Color 

(3)  Transparency 

(4)  Odor 

(5)  Specific  gravity 

(6)  Reaction  (whether  acid  or  alkaline) 

(7)  Albumin 

(8)  Sugar 

(9)  Microscopic  examination 

(1)   THE   AMOUNT 

The  amount  of  urine  passed  in  twenty-four  hours 
by  an  adult  or  child  above  eight  years  is  on  the  aver- 
age from  1000  to  2000  cubic  centimeters.  It  rep- 
resents about  60  or  70%  of  the  water  taken  in.     j 


116  CHEMISTRY   FOR   NURSES 

Measuring  Urine.  —  In  measuring  the  amount 
it  is  necessar}^  to  start  with  the  bladder  empty,  — 
that  is  to  say,  the  patient  should  void  just  before 
the  hour  at  which  the  twenty-four-hour  specimen  is  to 
be  commenced,  and  the  patient  must,  of  course,  empty 
the  bladder  again  just  before  the  end  of  the  twenty- 
four-hour  period,  so  that  the  actual  amount  formed 
by  the  kidneys  in  twenty-four  hours  is  obtained. 
The  urine  is  best  collected  in  a  2-quart  bottle  or  jar, 
kept  in  a  cool  place,  and  often  some  preservative  is 
added  (a  few  cubic  centimeters  of  chloroform  or 
toluol  or  a  few  crystals  of  thymol). 

Normal  Variations  in  Amount.  —  The  amount  of 
urine  varies  greatly,  even  in  health.  It  is  diminished 
in  warm  weather  and  in  fact  by  anything  which 
causes  much  perspiration.  It  is  increased  by  drink- 
ing copiously  and  by  anything  which  decreases  the 
amount  of  perspiration. 

Pathological  Variations  in  Amount.  —  The  obser- 
vation of  the  amount  is  of  importance  in  many  dis- 
eases. The  quantity  is  diminished  in  all  fevers  (due 
largely  to  the  much  greater  evaporation  from  the 
skin  in  fevers),  in  acute  nephritis  (acute  Bright ^s 
disease),  in  the  final  stage  of  chronic  nephritis,  and  in 
heart  failure.  It  is  also  diminished  in  all  diseases  in 
which  a  large  amount  of  water  is  lost  through  some 


URINE  117* 

other  part  of  the  body,  as  in  diarrhea  and  dysentery, 
in  hemorrhage,  and  in  vomiting. 

Suppression  of  the  urine  (or  failure  of  the  kidneys 
to  secrete  any  urine)  occurs  in  very  acute  forms  of 
nephritis,  —  such  as  nephritis  caused  by  certain 
poisons  like  mercury  and  carbolic  acid.  It  may  also 
occur  from  the  obstruction  of  the  ureter,  or  occa- 
sionally as  a  reflex  nervous  result  of  operation, 
injury,  or  disease  of  some  part  of  the  urinary 
tract. 

Retention  of  urine  means  failure  of  the  bladder  to 
empty  out  the  urine  which  has  been  secreted  by  the 
kidneys.  It  is  of  importance  practically  to  dis- 
tinguish between  retention  and  suppression.  Re- 
tention is  due  to  a  great  variety  of  different  causes, 
such  as  paralysis  of  the  bladder,  obstructions  of  the 
urethra  by  tumors,  by  a  large  prostate  gland,  by 
urinary  stones,  etc. 

Careful  measuring  of  the  amount  of  urine  by  the 
nurse  is  a  thing  of  the  greatest  possible  importance 
in  all  forms  of  kidney  disease  and  in  all  such  dis- 
eases (for  instance,  scarlet  fever)  as  are  likely  to  be 
complicated  by  kidney  disease.  In  such  cases  the 
increase  in  the  amount  of  urine  generally  means  that 
the  patient  is  improving  or  that  the  treatment  is 
effective.    It   is   always   desirable   to   measure   the 


118  CHEMISTRY   FOR  NURSES 

amount  of  fluids  taken  by  the  patient  so  that  it  can  be 
compared  with  the  amount  of  urine  excreted. 

The  amount  of  urine  is  increased  (this  is  called 
polyuria)  chiefly  in  three  diseases:  (1)  in  diabetes 
mellitus  (the  ordinary  form  of  diabetes  in  which 
sugar  is  found  in  the  urine),  (2)  in  diabetes  insipidus 
(the  disease  whose  principal  symptom  is  an  excretion 
of  large  amounts  of  urine),  (3)  in  chronic  Bright ^s 
disease. 

(2)    COLOR 

The  color  of  normal  urine  varies  greatly.  It  de- 
pends largely  on  the  amount  of  urine  excreted.  It 
varies  from  pale  straw  color  in  persons  who  are  pass- 
ing a  great  deal  of  urine  to  lemon  yellow  and  to  deep 
amber  color  in  persons  who  are  passing  a  small 
amount  of  urine.  High-colored  urine  occurs  par- 
ticularly in  fevers.  Abnormal  colors  are  caused  by 
a  number  of  different  things.  The  color  of  fresh 
blood  is  easily  recognized.  Very  small  amounts  of 
blood  give  a  smoky  appearance  without  actual  red 
color.  The  yellowish  green  color  given  to  urine  by 
hile  in  cases  of  jaundice  is  characteristic.  It  is  im- 
portant to  be  able  to  recognize  this  color,  as  there  are 
cases  of  liver  disease  in  which  the  amount  of  bile 
retained  by  the  body  is  too  small  to  cause  noticeable 


URINE  119 

jaundice  in  the  skin,  but  in  which  bile  nevertheless  is 
found  in  the  urine.  There  are  a  number  of  chemical 
tests  employed  by  doctors  to  detect  these  small 
traces  of  bile.  Urine  which  contains  bile  stains 
paper  or  linen  a  peculiar  yellow,  and  if  a  little  of  it 
is  shaken  up  in  a  test  tube,  a  foam  forms  on  the  top 
which  is  a  yellow  color, — whereas  the  foam  of  normal 
urine  is  white.  Urine  may  be  colored  reddish  after 
the  taking  of  certain  drugs  such  as  rhubarb,  senna, 
santonin  ;  or  colored  blackish  in  carbolic  acid  poison- 
ing, or  green  after  the  use  of  methylene  blue  as  a  drug. 

(3)   TRANSPARENCY 

Significance  of  Turbid  Urine.  —  Normal  urine  is 
perfectly  clear,  with  a  very  faint  cloud  of  mucus 
which  collects  if  the  urine  is  allowed  to  stand  for  a 
couple  of  hours.  The  turbidity  of  urine  is  an  im- 
portant thing  for  the  nurse  to  notice.  The  turbidity 
which  is  jpresent  when  the  urine  is  passed  is  the  only 
kind  that  is  of  any  practical  importance. 

Turbidity  which  occurs  in  urine  which  has  been 
standing  for  any  length  of  time  may  be  due  to  growth 
of  bacteria  in  the  urine  or  to  the  formation  of  various 
kinds  of  deposit,  such  as  deposits  of  phosphates  or 
substances  known  as  urates.  This  latter  urate  de- 
posit is  likely  to  be  brick  dust  in  color  and  is  very 


120  CHEMISTRY   FOR  NURSES 

common  in  urine  which  has  been  left  standing  in  the 
cold,  —  so  common,  in  fact,  that  it  has  been  very 
widely  used  in  fraudulent  advertisements  to  frighten 
healthy  people  into  thinking  that  they  had  kidney 
trouble  and  taking  some  patent  medicine.  It  is 
never  a  sign  of  disease.  It  is  easily  recognized  by  the 
fact  that  it  dissolves  if  the  urine  is  warmed. 

The  turbidity  which  is  due  to  the  growth  of  bac- 
teria is  accompanied  by  the  development  of  an  am- 
moniacal  smell  and  is  a  disturbing  factor  in  making 
several  of  the  special  tests  on  urine.  For  this  reason 
when  urine  cannot  be  sent  to  the  laboratory  at  once 
or  when  twenty-four  hour  specimens  are  collected, 
the  urine  should  be  kept  in  the  cold  (ice  box)  or  some 
harmless  preservative  should  be  added,  such  as 
chloroform,  thymol  crystals,  or  toluol.  As  some  of 
these  substances  may  have  an  effect  on  certain  chemi- 
cal tests,  it  should  always  be  noted  which  one  has 
been  added. 

In  urine  which  has  become  alkaline  on  standing 
there  may  be  a  heavy  deposit  of  phosphates  or  of 
carbonates.  This,  unlike  the  deposit  of  urates, 
does  not  disappear  on  warming,  but  does  dissolve 
if  acetic  acid  is  added. 

Turbidity  of  Fresh  Urine.  —  Urine  which  is  tur- 
bid when  passed  may  be  so  from  the  presence  of  pus 


URINE  121 

or  of  phosphates  or  carbonates.  This  occurs  espe- 
cially in  cystitis  (inflammation  of  the  bladder),  pye- 
litis (inflammation  of  the  pelvis  of  the  kidney),  and 
various  kidney  inflammations  (such  as  abscess  or 
tuberculosis),  or  the  turbidity  may  be  due  to  pus 
from  leucorrhea  or  gonorrhea.  Pus  settles  to 
the  bottom  in  an  hour  or  two  as  a  thick  creamy 
layer.  It  can  only  be  identified  with  certainty  by  a 
microscopic  examination. 

It  is  especially  important  to  watch  for  any  slight 
turbidity  of  the  urine  in  cases  in  which  a  cystitis  is 
likely^  to  develop,  for  instance,  in  cases  which  are 
being  catheterized  frequently.  The  important  tur- 
bidity of  course  is  due  to  pus.  Turbidity  which 
clears  up  promptly  on  warming  the  urine  over  a 
flame  (in  the  case  of  urates),  or  on  adding  a  little 
dilute  acetic  acid  (phosphates  and  carbonates)  is 
never  due  to  pus. 

(4)    ODOR 

The  odor  of  freshly  passed  urine  may  vary  from 
the  normal,  especially  after  eating  certain  articles 
of  diet  such  as  asparagus.  Urine  which  is  foul  when 
passed  usually  comes  from  a  case  of  cystitis,  or  if  the 
odor  is  fecal,  from  a  case  of  fistula  connecting  the 
bladder  and  rectum.    On  being  allowed  to  stand  for 


122  CHEMISTRY   FOR   NURSES 

a  day  or  more  urine  becomes  foul-smelling  from  de- 
composition caused  by  bacteria. 

(5)   REACTION 

The  reaction  of  urine  is  tested  with  litmus  paper 
(see  Chapter  V).  Normal  urine  is  usually  acid,  or 
sometimes  amphoteric ;  that  is,  turning  red  litmus 
paper  blue  and  blue  litmus  paper  red.  Occasionally 
when  passed  after  a  heavy  meal  it  is  found  to  be 
slightly  alkaline,  due  to  the  fact  that  the  body  is 
using  up  the  acid  which  ordinarily  is  excreted  in  the 
urine  to  manufacture  the  acid  needed  by  the  stomach 
for  digestion.  This  is  known  as  the  alkaline  tide  in 
the  urine.  Urine  may  also  be  made  alkaline  by  the 
giving  of  alkaline  drugs  such  as  bicarbonate  or 
citrate  of  soda.  Aside  from  these  instances  urine 
which  is  alkaline  when  passed  is  generally  urine  de- 
composed as  the  result  of  cystitis.  Urine  which  has 
decomposed  after  being  passed  also  becomes  alkaline. 
The  alkalinity  of  decomposed  urine  is  due  to  the 
production  of  ammonia  (NHg)  by  the  action  of  a  cer- 
tain bacterium, — the  micrococcus  urei,  which  grows 
on  urea. 

(6)    SPECIFIC  GRAVITY 

What  is  Meant  by  Specific  Gravity.  —  The  specific 
gravity  of  urine  means  its  density,  or  what  is  the 


URINE  123 

same  thing,  the  weight  of  any  volume  of  urine  as 
compared  with  the  weight  of  an  exactly  equal  volume 
of  distilled  water.  Suppose  we  have  two  flasks  each 
containing  1000  c.c.  of  distilled  water,  their  weight 
exactly  the  same.  If  in  the  one  flask  we  dissolve 
10  grams  of  salt  then  the  water  in  that  flask  will 
weigh  10  grams  more  than  that  in  the  other  flask.  In 
other  words,  its  specific  gravity  will  be  1010.  Hence 
the  figure  that  represents  the  specific  gravity  of 
urine  really  indicates  to  us  the  number  of  grams 
of  solid  substance  dissolved  in  1000  c.c.  of  urine. 
The  specific  gravity  varies  in  health,  depending 
always  on  the  amount  of  urine  secreted ;  so  that  the 
figure  representing  the  specific  gravity  really  means 
very  little  unless  we  know  how  much  urine  is  secreted. 
If  we  do  know,  then  we  can  judge  whether  the  patient 
is  excreting  enough  solid  matter  or  not.  The  most 
important  solid  matters  to  be  excreted  are  urea  and 
salts.  When  the  kidneys  are  diseased  they  are  un- 
able to  excrete  sufficient  of  these  substances. 

Cause  of  Dropsy.  Reason  for  Salt^free  Diet.  — 
In  Chapter  VII  it  was  explained  why  it  is  very  impor- 
tant for  the  body  to  maintain  the  concentration  of 
salt  in  the  blood  at  precisely  a  certain  point.  If 
the  kidneys  are  unable  to  get  rid  of  the  surplus  salt, 
then  in  order  to  keep  the  concentration  of  the  body 


124  CHEMISTRY   FOR   NURSES 

fluids  right,  the  body  has  to  retain  water  also.  This 
leads  to  edema  or  dropsy.  This  is  the  reason  for 
salt-free  diet,  or  salt-poor  diet,  in  cases  of  kidney 
disease. 

The  normal  specific  gravity  of  the  urine  is  between 
1012  and  10^4-  The  specific  gravity  is  low  in  chronic 
Bright's  disease,  in  diabetes  insipidus,  and  after 
drinking  large  amounts  of  fluid.  The  specific  grav- 
ity is  high  when  the  amount  of  urine  excreted  is 
small,  as  in  fevers ;  it  is  high  especially  in  diabetes 
in  spite  of  the  large  amount  of  urine  passed,  due  to 
the  sugar  dissolved  in  the  urine. 

Method  of  Determining  Specific  Gravity.  —  In 
practice,  in  order  to  measure  the  specific  gravity  of 
urine  we  do  not  weigh  it,  but  we  use  a  much  simpler 
method  the  principle  of  which  depends  on  the  fact 
that  when  anything  floats  in  water  in  which  salts  or 
any  other  solid  substances  are  dissolved  it  is  buoyed  up 
and  floats  higher  than  it  would  in  plain  water.  Thus 
in  the  Dead  Sea  there  is  so  much  solid  matter  dis- 
solved that  a  person  cannot  sink.  To  measure  the 
specific  gravity  a  special  little  instrument  or  buoy 
called  a  urinometer  is  used.  It  is  dropped  into  the 
urine  and  made  to  float  there  without  touching  the 
sides  of  the  vessel.  Its  stem  which  projects  above 
the  surface  of  the  urine  has  marks  on  it  at  different 


URINE  125 

levels  and  these  marks  are  labeled  1000,  1010,  1020, 
1030,  and  so  on,  and  the  intermediate  figures  are  in- 
dicated by  strokes.  One  can  tell  the  specific  gravity 
of  the  urine  simply  by  reading  off  the  level  to  which 
this  stem  sinks  in  the  urine. 

(7)    ALBUMIN 

Heat  Test  for  Albumin.  —  One  of  the  most  im- 
portant things  which  urine  is  tested  for  is  albiunin. 
There  are  a  great  many  different  tests ;  the  heat  test 
is  the  simplest  and  is  very  delicate.  The  test  con- 
sists of  pouring  some  of  the  clear  urine  into  a  test 
tube  and  boiling  the  upper  layer  of  the  urine,  then 
adding  a  few  drops  of  weak  acetic  acid  (2%)  and 
boiling  again.  If  there  is  albumin  present,  a  very 
faint  or  heavy  cloudiness  (precipitate  of  coagulated 
albumin)  forms  on  boiling  and  persists  or  becomes 
heavier  on  adding  a  few  drops  of  dilute  (2%)  acetic 
acid  and  boiling  again.  //  a  precipitate  occurs  at 
the  first  boiling  hut  clears  up  again  entirely  on  adding 
acetic  acid,  it  is  not  albumin,  but  harmless  phosphates 
or  carbonates.  In  case  the  urine  is  alkaline  before 
the  test  is  made  it  must  first  be  neutralized  by  adding 
a  little  weak  acetic  acid.  In  case  the  urine  is  not 
clear  before  the  test  is  done  it  must  first  be  clarified 
by  filtration. 


126  CHEMISTRY   FOR   NURSES 

Significance  of  Albumin.  —  Albumin  in  the  urine 
generally  means  disease  of  some  sort.  The  most 
important  disease  in  which  it  occurs  of  course  is 
nephritis  (Bright 's  disease).  In  acute  nephritis  it 
occurs  in  large  amounts,  in  chronic  nephritis  in  mere 
traces.  When  the  heart  is  weak  and  also  in  fevers 
there  may  be  traces  of  albumin  in  the  urine  without 
the  kidneys  being  necessarily  diseased.  During 
pregnancy  an  occasional  test  of  the  urine  is  of  great 
importance  on  account  of  the  danger  of  kidney  com- 
plications. Urine  which  has  pus  in  it  or  blood  has 
of  course  also  albumin.  This,  however,  does  not 
necessarily  mean  kidney  disease. 

(8)    SUGAR 

Sugar  is  found  in  the  urine  chiefly  in  cases  of  dia- 
betes mellitus.  In  healthy  people,  however,  small 
amounts  of  sugar  may  occasionally  appear  in  the 
urine  under  special  circumstances,  —  such  as  after 
eating  an  excessive  amount  of  carbohydrates.  Oc- 
casionally in  pregnancy  or  during  lactation,  or  par- 
ticularly when  lactation  is  suddenly  ended,  milk 
sugar  is  found  in  the  urine.  The  sugar  found  in  the 
urine  in  diabetes  is  the  same  which  normally  is 
present  in  the  blood;  namely,  dextrose  (glucose, 
grape  sugar). 


URINE  127 

Fehling^s  test  for  sugar  in  the  urine  is  the  one  usu- 
ally used.  The  fermentation  test  is  also  often  used. 
Both  tests  are  described  in  Chapter  IX.  The  fermen- 
tation test  is  of  aid  in  distinguishing  between  dex- 
trose and  milk  sugar :  milk  sugar  is  not  fermented 
by  yeast  but  gives  reduction  with  Fehling's  test. 

The  Amount  of  Sugar.  —  The  amount  of  sugar  in 
the  urine  is  one  of  the  most  important  things  for  the 
doctor  to  know  in  treating  a  case  of  diabetes ;  and 
as  in  these  cases  the  amount  passed  by  the  kidneys 
at  different  hours  of  the  day  varies,  the  only  figure 
that  has  any  meaning  is  the  total  amount  of  sugar  lost 
by  the  body  in  twenty-four  hours.  This  in  turn  is  only 
of  significance  when  it  can  be  compared  with  the  total 
amount  of  carbohydrates  eaten  by  the  patient  in  the 
same  twenty-four  hours.  For  this  reason  the  mere 
percentage  of  sugar  in  one  specimen  or  urine  really 
means  very  little.  It  is  not  necessary  for  nurses  to 
learn  the  methods  of  measuring  the  amount  of  sugar. 

Acetone  and  Diacetic  Acid. — Besides  sugar  there 
are  two  other  things  which  are  always  extremely 
important  to  test  for  in  the  urine  of  patients  who 
have  diabetes ;  these  are  acetone  and  diacetic  acid. 
In  diabetes  death  most  commonly  results  from  the 
so-called  acid  intoxication  or  diabetic  coma.  This 
comes  from  the  accumulation  of  certain  acids  in  the 


128  CHEMISTRY   FOR   NURSES 

body,  and  the  presence  of  these  acids  in  the  blood 
is  shown  by  acetone  or  diacetic  acid  appearing  in 
the  urine.  These  same  substances  may  also  be 
found  in  the  urine  during  starvation  or  in  diseases 
in  which  the  nourishment  of  the  patient  is  very 
greatly  cut  down.  There  are  very  few  chemical 
tests  that  nurses  ever  are  called  on  to  perform,  but 
the  test  for  diacetic  acid  is  so  simple,  and  knowing 
whether  it  is  present  in  a  given  case  of  diabetes  from 
day  to  day  is  so  important,  that  the  test  will  be  men- 
tioned here.  If  to  a  few  drops  of  urine  containing 
diacetic  acid  an  excess  of  ferric  chloride  solution  is 
added,  the  fluid  becomes  a  Bordeau  red  (red  wine) 
color.  This  color  disappears  or  gets  fainter  if  the 
urine  is  boiled.  (Adding  an  excess  of  ferric  chloride 
solution  means  adding  more  ferric  chloride  solution 
than  there  is  urine  in  the  tube.) 

Reason  for  Alkaline  Medication.  —  When  these 
acids  are  found  in  the  urine,  as  a  rule  alkalies  are 
ordered  as  medicines  (sodium  bicarbonate,  sodium 
citrate)  and  the  diet  is  made  much  more  liberal  even 
if  the  amount  of  sugar  excreted  becomes  greater.  In 
such  cases  the  doctor  sometimes  puts  litmus  paper 
in  the  hands  of  the  nurse  and  instructs  her  to  give 
the  alkaline  medication  at  regular  intervals  untiJ 
the  urine  becomes  and  remains  alkaline. 


URINE  129 

(9)   MICROSCOPIC  EXAMINATION 

Nurses  are  never  called  upon  to  do  a  microscopic 
examination  of  urine,  but  as  such  examinations  are 
often  done  on  the  patients  that  they  are  taking  care 
of,  they  should  know  what  is  meant  by  a  few  of  the 
tepns  used.  In  a  microscopic  examination  the  most 
important  things  looked  for  are  pus,  blood  cells,  and 
casts.  Pus  is  recognized  by  the  finding  of  so-called 
pus  cells,  which  are  nothing  but  dead  leucocytes 
(white  blood  cells).  The  finding  of  red  Uood  cells 
in  urine  is  of  great  diagnostic  value  especially  when 
kidney  stones  are  suspected.  Small  numbers  of  the 
blood  cells  are  often  found  in  urine  that  is  not  the 
least  blood  tinged.  When  urine  is  to  he  examined 
for  hlood  cells  it  rruast  he  examined  fresh,  as  the  red  cells 
lose  their  outlines  and  are  almost  impossible  to  rec- 
ognize after  the  urine  has  been  standing  for  a  day. 
Casts  in  the  urine  always  point  to  kidney  disease. 
Casts  are  very  minute  cylindrical  bodies  molded  to 
the  shape  of  the  inside  of  the  fine  kidney  tubules  in 
which  the  urine  is  secreted.  They  are  composed  of 
albumin  which  is  coagulated  or  solidified  in  the  tubules. 
When  present  in  large  numbers  they  are  of  very  grave 
significance.  Beside  these  things  the  urine  frequently 
contains  crystals  of  various  kinds,  and  bacteria. 


CHAPTER  XIV 

Stomach  Contents  and  Feces 

STOMACH  contents 

Nurses  are  not  expected  to  make  chemical  anal- 
yses, but  as  they  frequently  have  to  assist  doctors 
in  securing  samples  of  stomach  contents,  and  as  they 
have  to  make  careful  notes  of  the  appearance  of 
vomitus,  they  should  know  something  about  the 
examination  of  gastric  juice. 

Object  of  Examining  Stomach  Contents.  —  In  the 
examination  of  the  stomach  contents  much  depends 
on  the  time  and  circumstances  under  which  the 
specimen  is  obtained.  Ordinarily  we  desire  to  find 
out  how  the  stomach  behaves  in  a  definite  number 
of  minutes  after  the  taking  of  a  definite  kind  of  test 
meal.  Frequently  we  wish  to  find  out  whether  the 
stomach  is  capable  of  emptying  itself  in  a  certain  num- 
ber of  hours.  This  is  the  object  of  the  taking  of  the 
stomach  contents  in  the  early  morning  before  any 
food  is  taken.  The  normal  stomach  should  be 
practically  empty  at  this  time  of  day.    If  there  is 

130 


STOMACH  CONTENTS  AND  FECES       131 

much  fluid  in  it,  —  especially  if  there  are  any  rem- 
nants of  food  taken  the  day  before,  —  then  we  know 
that  there  is  some  delay  in  the  emptying  of  the  stom- 
ach into  the  intestine. 

Is  the  Pylorus  Obstructed?  —  When  this  question 
is  to  be  determined,  usually  some  easily  recognized 
kind  of  food  such  as  raisins,  cranberry  or  currant 
preserves,  or  a  few  grains  of  rice  are  given  the  night 
before.  The  kind  of  food  remnants  recognizable  in 
the  stomach  contents  or  vomitus  should  be  noted  by  the 
nurse  and  she  should  report  how  long  before  the  kind 
of  food  seen  was  taken. 

The  quantity  of  the  stomach  contents  should  always 
be  accurately  measured;  an  abnormally  large  amount 
means  either  obstruction  at  the  pylorus  or  an  exces- 
sive secretion.  ^  After  a  test  meal  usually  50  to  100 
c.c.  are  obtained. 

Gross  Appearance.  —  Other  facts  in  the  gross  ap- 
pearance are  also  worth  noting:  whether  (after 
an  Ewald  test  breakfast)  the  bread  is  chewed  or  not, 
—  whether  there  is  bile  present  or  not,  —  and  above 
all  whether  there  is  any  trace  of  blood. 

Blood  in  Stomach  Contents.  —  Blood  in  the  stom- 
ach contents  looks  brovm  or  black,  and  if  there  is  much, 
it  has  a  coffee  grounds  appearance  due  to  the  action  of 
the  hydrochloric  acid  of  the  stomach  on  the  haemo- 


132  CHEMISTRY   FOR  NURSES 

globin  of  the  blood.  Bright  red  streaks  of  blood  in  the 
stomach  contents  almost  always  come  from  the 
mouth  or  throat ;  and  they  should  always  he  noted  hy 
the  nursej  because  if  they  subsequently  become  af- 
fected by  the  acid  and  dissolved  in  the  remainder  of 
the  stomach  contents,  they  may  deceive  the  doctor 
who  makes  the  examination  later.  Blood  can  be 
tested  for  by  chemical  means  and  an  extremely 
minute  trace  of  it  can  be  detected.  Its  finding  is  of 
great  importance  and  usually  points  either  to  an 
ulcer  or  a  cancer  of  the  stomach. 

Acidity.  —  Next  to  the  finding  of  blood  the  most 
important  practical  examination  of  the  stomach  con- 
tents is  the  measuring  of  the  amount  of  acid.  This  is 
measured  in  terms  of  the  number  of  cubic  centimeters 
of  a  particular  strength  of  sodium  hydrate  (called  deci- 
normal  sodium  hydrate)  which  100  c.c.  of  the  stomach 
contents  will  neutralize.  Thus  a  doctor^s  report  that 
the  acidity  of  the  stomach  contents  is  60  means  that 
100  c.c.  of  the  stomach  contents  have  enough  acid 
to  neutralize  60  c.c.  of  this  kind  of  alkali.  The 
amount  of  acid  is  increased  in  certain  kinds  of  stom- 
ach troubles,  and  especially  in  ulcer  of  the  stomach. 
It  is  diminished  in  certain  other  stomach  troubles, 
and  especially  in  cancer.  In  some  diseases  the  ordi- 
nary hydrochloric  acid  of  the  stomach  is  almost 


STOMACH   CONTENTS   AND   FECES  133 

absent  and  a  different  kind  of  acid,  namely  lactic 
acid,  is  found ;  it  is  produced  by  the  fermentation  of 
food  through  the  agency  of  bacteria.  Lactic  add 
gives  a  sour  odor  which  the  nurse  can  often  learn  to 
recognize. 

As  the  saliva  is  alkaline,  it  is  of  great  importance  not 
to  get  any  saliva  mixed  with  the  stomach  contents ;  if 
any  is  accidentally  mixed  in  during  the  obtaining  of 
the  stomach  contents,  one  should  make  note  of  the 
fact ;  otherwise,  especially  if  the  amount  of  the 
stomach  contents  is  small  and  the  amount  of  saliva 
considerable,  the  examination  of  the  acidity  may 
be  entirely  misleading. 

EXAMINATION  OF  FECES 

The  examination  of  the  feces  is  a  thing  in  which 
the  nurse  is  sometimes  of  assistance.  Only  one  or 
two  points  need  to  be  discussed.  The  most  impor- 
tant single  thing  examined  for  is  hlood;  it  has  the  same 
significance  here  as  in  the  stomach  contents ;  namely, 
ulceration  of  some  kind  in  the  stomach  or  intestine. 
Large  amounts  of  blood  of  course  are  easily  seen. 
Minute  traces  are  detected  by  very  delicate  chemical 
tests  (benzidine  reaction).  As  any  blood  taken 
with  meat  will  also  give  a  positive  chemical  test  for 
blood,  the  patient  has  to  he  put  on  a  meat-free  diet  for 


134  CHEMISTRY   FOR  NURSES 

three  days  before  one  can  be  sure  that  a  positive 
chemical  test  for  blood  in  the  stool  really  means  a 
little  bleeding  into  the  intestines  or  stomach. 

Significance  of  Fatty  Stools.  —  Aside  from  the 
observation  of  blood  the  question  of  whether  bile  is 
present  or  not  is  of  much  practical  importance.  In 
cases  of  jaundice  when  the  bile  does  not  empty  into 
the  intestines  the  stools  are  of  a  pale  gray  or  slate 
color  and  of  a  pasty  consistency.  This  is  due  not 
only  to  the  absence  of  the  pigments  derived  from  bile 
in  the  stools  but  chiefly  to  the  large  amount  of  un- 
digested fat.  It  will  be  remembered  that  bile  plays 
an  important  part  in  aiding  the  digestion  of  fat  by 
emulsifying  it.  This  is  the  reason  that  patients  who 
have  obstructive  jaundice  have  to  get  their  nourish- 
ment largely  from  carbohydrates  and  proteids,  and 
the  amount  of  fat  in  their  diet  is  to  be  restricted. 


INDEX 


Acetate,  lead,  9 
Acetates,  63 
Acetic  acid,  36,  63 
Acetic  fermentation,  73 
Acetone,  127 
Acid,  acetic,  .36,  63 
amino,  91,  100,  112 

effect  of  erepsin  on.  111 
effect  of  trypsin  on,  109 
benzoic,  62 
boric,  7 
butyric,  63 
carbolic,  62 
carbonic,  42 
citric,  36,  63 
diacetic,  127 
hydrochloric,  36 

absence  in  stomach  contents, 

132 
presence  in  stomach  contents, 
105 
hydrofluoric,  42 
lactic,  63 

in  stomach,  133 
nitric,  36 
action  of,  41 
test  for  proteids,  97 
oleic,  63 
oxalic,  63 
phosphoric,  37 
salicylic,  62 
sulphuric,  36 
tartaric,  63 
uric,  114 
Acid  intoxication,  127 
Acids,  86,  63 
fatty,  63 
of  milk  fat,  110 
organic,  42,  56,  62 
power  of  neutralizing,  45 
Aflanity,  chemical,  21 
Air,  35 


Albumin,  125 

coagulation  test  for,  95 
Albuminoids,  93 
Albumins,  92 
Alcoholic  fermentation,  73 
Alcohols,  63 

Alkaline  medication,  128 
Alkaloids,  63 
Aluminium,  7 
Amino  acid,  91,  100,  112 

effect  of  erepsin  on,  111 

effect  of  trypsin  on,  109 
Ammonia,  44,  50 

composition  of,  25 

in  urine,  122 
Ammonium  hydrate,  44 
Amylase,  103,  108 
Analysis,  6 
Animal  starch,  78 
Animals,  carnivorous,  98 

herbivorous,  98 
Argyrol,  11 

Aromatic  substances,  62 
Arsenic,  7 
Arterial  blood,  35 
Atomic  theory,  12 
Atoms,  13 

weight  of,  14 
Atropine,  64 


Bacteria,  71 

discovery  of,  73 

nitrifying,  98 
Bacterial  spores,  95 
Bases,  44,  45 

organic,  63 
Basic  salt,  55 
Beets,  69 

Benzidine  reaction,  133 
Benzine,  84 
Benzoic  acid,  62 
Benzol,  62 


135 


136 


INDEX 


Bicarbonate,  sodium,  52,  55 
Bichloride   of   mercury,    sterilizing 

effect  of,  96 
Bile,  108 

in  feces,  134 

use  of,  110 
Biological  chemistry,  58 
Bismuth,  7 

subnitrate,  51 
Blood,  arterial,  35 

effect  of  distilled  water  on,  53 

in  stomach  contents,  131 

venous,-  35 
Blood  clot,  93 
Blood  serum,  93 
Bone,  8,  10 
Borax,  7 
Boric  acid,  7 
Boron,  7 

Bread,  leavening  of,  72 
Bright's  disease,  126 
Bromides,  7 
Bromine,  7 
Bunsen  flame,  33 
Butter,  cocoa,  80 

peanut,  80 
Butyric  acid,  63 


Calcium,  7,  10 
Calcium  chloride,  55 
Calcium  hydrate,  44 
Calcium  phosphate,  7,  10 
Calomel,  9 
Calorie,  31 
Camphor,  62 
Cane  sugar,  69,  70 
Carbohc  acid,  62 
Carbon,  8,  60 
Carbon  dioxide,  20,  25,  72 
Carbonates,  list  of,  52 
Carbonic  acid,  42 
Carbohydrates,  65 
Carnivorous  animals,  98 
Casein,  93 
Caseinogen,  93 
Castile  soap,  86 
Casts  in  urine,  129 
Caustic  potash,  10,  44 
Caustic  soda,  44,  46 
Caustic  stick,  41 


Cellulose,  75,  76 

Cereals,  amount  of  fat  in,  80 

Cheese,  73,  93 

Chemical  affinity,  21 

Chemical  elements,  2 

Chemical  formulas,  22 

Chemistry,  biological,  58 

organic,  56 

synthetic,  58 
Chloride,  calcium,  56 

silver,  22,  42 

sodium,  3,  49 

zinc,  39 
Chlorides,  18 

list  of,  51 
Chlorine,  8 
Chloroform,    as    preservative    for 

urine,  120 
Citrates,  63 
Citric  acid,  36,  63 
Clay,  10 
Cleansing,  88 
Clot,  blood,  93 
Coagulation,  9^,  96 

of  milk,  105 

test  for  albumin,  95 
Cocaine,  63 
Cocoa  butter,  80 
Codeine,  63 
Collagen,  93 
Coma,  diabetic,  127 
Combustion,  32,  56 
Compound  proteids,  93 
Compounds,  2 
Conservation  of  energy,  29 
Cooking,  94 
Copper,  8 

Copper  sulphate,  51 
Cotton,  78 
Cotton-seed  oil,  80 
Crystallization,  16 
Curd,  93 
Cystitis,  121 


Dextrin,  75,  77 
Dextrose,  67,  68,  77 

action  of  yeast  on,  72 

in  urine,  126 
Diabetes,  sugar  in,  .126 
Diabetes  insipidus,  118 


INDEX 


137 


Diabetes  mellitus,  118 
Diabetic  coma,  127 
Diacetic  acid,  127 
Diastase,  70 

action  on  starch,  103 
Diet,  meat-free,  133 

salt-free,  123 
Digestion,  101,  78 

by  malt  extract,  77 

effect  of  acids  on,  105 

gastric,  105 

pancreatic,  108 

starch,  104 
Dioxide,  carbon,  20,  25,  72 

test  for,  34 
Disaccharides,  67,  70 

list  of,  69 
Disinfection  of  skin,  87 
Distillation,  17 

Distilled  water,  effect  on  blood,  53 
Dropsy,  123 
Dynamo,  29 


Egg  white,  93 

Einhorn  fermentation  tubes,  72 

Elements,  chemical,  2 

halogen,  52 

list  of,  6,  7 
Emulsification  of  fats.  111 
Emulsion,  84,  88 
Energy,  "27 

as  a  mode  of  motion,  28 

conservation  of,  29 

fat,  as  source  of,  79 

hidden,  29 
Enzymes,  101 

chemical  nature  of,  102 

synthetic  action  of,  103 
Epsom  salt,  51 
Erepsin,  111 
Ether,  84 
Evaporation,  17 
Extract,  malt,  70 

meat,  99 


Fat,  a  source  of  energy,  79 
amount  in  cereals,  80 
amount  in  nuts,  80 


Fat,  digestion  of,  109 

emulsification  of.  111 
Fatty  acids,  63 

of  mUk  fat,  110 

soaps  from.  111 
Fatty  stools,  in  jaundice.  111,  134 
Feces,  bile  in,  134 
Fehling's  test,  70,  74 
Fermentation,  71 

acetic,  73 

alcoholic,  73 

by-products  of,  72 

gastro-intestinal,  74 

lactic  acid,  73 
Fermentation  tubes,  Einhom,  72 
Fibrinogen,  93 
Filtering,  22 
Filtrate,  22 
Flash  light,  9 
Food  value,  31 
Formulas,  chemical,  22 

structural,  26 
Fructose,  67 
Fruit  sugar,  67,  68 

plan  of  molecule,  69 


Gas,  laughing,  17 

Gases,  solubility  of,  17 

Gasoline,  84 

Gastric  digestion,  105 

Gastro-intestinal  fermentation,  74 

Gelatin,  93 

Glassware,  10 

Globiilins,  92 

Glucose,  67,  68 

in  urine,  126 
Gluten,  93 
Glycerin,  63,  81 
Glycogen,  75,  78 
Glycosuria,  74 
Gold,  8 
Grape  sugar,  67,  68 

plan  of  molecule,  61 
Grease  spots,  83 
Green  soap,  86 


Haemoglobin,  8,  35,  93 
Haemolysis,  54 


138 


INDEX 


Hair,  burnt,  93 
Halogen  elements,  52 
Hard  soap,  87 
Hard  water,  88 
Heat,  28 

sterilizing  effect  of,  96 
Heat  test  for  albumin,  126 
Herbivorous  animals,  98 
Hidden  energy,  129 
Honey,  69 
Hydrate,  ammonium,  44 

calcium,  44 

potassium,  10,  44 

sodium,  44 
Hydrates,  44 

Hydrochloric     acid,     absence     in 
stomach  contents,  132 

presence    in    stomach    contents, 
105 
Hydrofluoric  acid,  42 
Hydrogen,  8 

peroxide  of,  5 
Hydroxide,  sodium,  46 
Hydroxides,  46 
Hypotheses,  uses  of  in  science,  12 


Indigo,  62,  90 
Intestinal*  fermentation,  74 
Intestinaleecretion,  111 
Intoxication,  acid,  127 
Iodide,  potassium,  20 
Iodides,  8 

Iodine  test  for  starch,  77 
Iron,  rusting  of,  32 


Jaundice,  stools  of.  111,  134 
urine  in,  118 


Keratin,  93 

Kidneys,  functions  of,  113 

Kumiss,  73 


Lactates,  63 

Lactic  acid,  in  stomach,  133 


Lactic  acid  fermentation,  73 

Lactose,  69,  75 

Laughing  gas,  18 

Lead,  9 

Lead  acetate,  9 

Leavening  of  bread,  72 

Legumen,  93 

Lemons,  63 

Levulose,  67,  68 

Limestone,  7 

Limewater,  34,  44 

Linen,  78 

Lipase,  109 

Lithium,  9 

Litmus  solution,  109 

Litmus  test,  43,  44 

Liver,  78 

M 

Magnesia,  milk  of,  9 

Magnesium,  9 

Malt  extract,  70 

Malt  soup,  70 

Malt  sugar,  69 

Malted  milk,  70 

Maltose,  69,  70,  77 

Maple  sugar,  69 

Marble,  7 

Matzoon,  73 

Meal,  test,  130 

Meat,  93 

Meat  extract,  99 

Meat-free  diet,  133 

Medication,  alkaline,  128 

Menthol,  62 

Mercury,  9 

sterilizing  effect  of  bichloride,  96 
Metabolism,  diseases  of,  59 
Microscopic  examination,  129 
Milk,  as  example  of  emulsion,  84 

coagulation  of,  105 

malted,  70 

of  magnesia,  9 

sour,  63,  73 
Milk  sugar,  69 
Milk  whey,  93 
Mineral  substances,  56 
Molecule,  plan  of  fruit  sugar,  69 

plan  of  grape  sugar,  61 
Molecules,  12 

size  of,  14 


INDEX 


139 


Monosaccharides,  66 

list  of,  67 
Morphine,  63 

Motion,  energy  as  mode  of,  28 
Mucin,  93 
Mucua,  93 
Myosin,  93 

N 

Naphtha,  84 

Nephritis,  126 

Neutral  point,  49 

Neutral  salt,  55 

Neutralization,  48 

Nickel,  9 

Niter,  51 

Nitrate,  silver,  22,  39 
formula  for,  20 
sterilizing  effect  of,  96 
structural  formula,  26 
test  for  presence  of,  41 

Nitrates,  list  of,  51 

Nitric  acid,  36 
action  of,  41 

'   test  for  proteids,  97 

Nitrifying  bacteria,  98 

Nitrogen,  9 

Nitrogen  starvation,  98 

Normal  salt  solution,  63 

Nuts,  fat  in,  80 


Oil,  cotton-seed,  80 

olive,  80 
Oleic  acid,  63 
Organic  acids,  42,  56,  62 
Organic  bases,  63 
Organic  chemistry,  66 
Oxalates,  63 
Oxalic  acid,  63 
Oxidation,  81,  32 
Oxides,  18 
Oxygen,  9,  32 


Pancreatic  digestion,  108 
Pancreatin,  109 
Paper,  78 
Peanut  butter,  80 


Pepsin,  105,  106 
Peptones,  99 

test  for,  108 
Peroxide  of  hydrogen,  6 
Phenacetine,  62 
Phenol,  62 
Phosphate,  calcium,  7,  10 

sodium,  10,  55 
Phosphates,  list  of,  52 
Phosphoric  acid,  37 
Phosphorus,  10 
Plants,  woody  part  of,  78 
Plaster  of  Paris,  51 
Platinum,  10 
Polarized  light,  68 
Polypeptids,  100 

effect  of  trypsin  on,  109 
Polysaccharides,  67 

list  of,  75 
Potash,  caustic,  10,  44 
Potassium,  10 
Potassium  hydrate,  10,  44 
Potassium  iodide,  20 
Powder,  baking,  63 
Precipitate,  22,  41 
Preservative  for  urine,  120 
Protargol,  11 
Proteid,  test  for,  96 
Proteids,  90 

compound,  93 

elementary  composition  of,  19 

nitric  acid  test  for,  97 

simple,  92 
Proteoses,  99 

test  for,  108 
Ptyalin,  103 
Pus  in  urine,  121 
Pyelitis,  121 


Quinine,  62 


Radiimi,  10 
Reaction  of  urine,  122 
Reduction,  74 
Rennin,  105,  106 
Residue,  22 
Respiration,  35 
Retention  of  urine.  117 


140 


INDEX 


Rock,  10 
Rubber,  90 
Rusting  of  iron,  32 

S 

Saccharine,  69 
Saccharose,  69 
Salicylic  acid,  62 
Saliva,  103 
Salt,  Epsom,  51 
Salt,  formation  of,  48 

in  the  body,  53 

neutral,  55 

table,  3,  49,  56 
Salt  balance,  114 
Salt-free  diet,  123 
Saltpeter,  51 
Salts,  Jf2,  50 

acid,  55 

basic,  55 
Sand,  10 

Saturated  solution,  16 
Scrubbing  up,  87 
Secretion,  intestinal,  111 
Serum,  blood,  93 
Silicon,  10 
Silver,  11 

Silver  chloride,  22,  42 
Silver  nitrate,  22,  39 

formula  for,  20 

sterilizing  effect  of,  96 

structural  formula,  26 

test  for  presence  of,  41 
Skin,  disinfection  of,  87 
Soap,  Castile,  86 
Soap,  cleansing  power  of,  88 

green,  86 

hard,  87 

manufacture  of,  85 

soft,  87 
Soaps,  85 

from  fatty  acids,  111 
Soda,  bicarbonate  of,  22,  65 

caustic,  44,  46 
Sodium,  11 

Sodium  bicarbonate,  52,  55 
Sodiunj  chloride,  3,  49 
Sodium  hydrate,  44 
Sodium  hydroxide,  46 
Sodium  phosphate,  10,  55 
Soft  soap,  87 


Solubility  of  gases,  17 
Solution,  litmus,  109 

normal  salt,  53 

saturated,  16 
Soup,  malt,  70 
Sour  mHk,  63,  73 
Specific  gravity,  122 
Spores,  bacterial,  95 
Starch,  75,  76 

action  of  diastase  on,  103 

animal,  78 

effect  of  ptyalin  on,  103 

iodine  test  for,  77 
Starch  digestion,  104 
Starch  digestion  by  malt  extract, 

77 
Starch  digestion,  effect  of  acids  on, 

105 
Starvation,  nitrogen,  98 
Steam  engine,  28 
Steam  sterilization,  95 
Sterilization,  heat,  95 

steam,  95 
Sterilizing   effect   of    bichloride   of 

mercury,  96 
Sterilizing  effect  of  heat,  95 
Sterilizing  effect  of  silver  nitrate,  96 
Stick,  caustic,  41 
Stomach,  lactic  acid  in,  133 
Stomach,   absence  of  hydrochloric 
acid  in,  132 

blood  in,  131 

contents,  130 

digestion  in,  105 ; 

lactic  acid  in,  133 

presence  of  hydrochloric  acid  in, 
105 
Stools,  fatty,  in  jaundice.  111,  134 
Strontium,  11 
Structural  formulas,  26 
Strychnine,  63 
Subnitrate,  bismuth,  51 
Sucrose,  69 
Sugar,  56,  126 

cane,  69,  70 

fruit,  67,  68,  69 

grape,  67,  68 

grape,  plan  of  molecule,  61 

in  diabetes,  126 

malt,  69 

maple,  69 

milk,  69 


INDEX 


141 


Sugars,  classification  of,  66 

properties  of,  71 

simple,  67 

tests  for,  74 
Sulphate,  copper,  51 

zinc,  11 
Sulphates,  list  of,  51 
Sulphocarbolate,  zinc,  11 
Sulphur,  11 
Sulphuric  acid,  36 
Suppression  of  urine,  117 
Synthesis,  6 

Synthetic  action  of  enzymes,  103 
Synthetic  chemistry,  58 


Table  salt,  3,  49 
Tartaric  acid,  63 
Tartrates,  63 
Test,  Fehling's,  70,  74 

litmus,  43,  44 
Test  meal,  130 
Theory,  atomic,  12 
Thymol  as  preservative  for  urine, 

120 
Tin,  115 

Tincture  of  green  soap,  86 
Toluol,  as  preservative  for  urine, 

120 
Trypsin,  108 

effect  on  amino  acids,  109 
effect  on  polypeptids,  109 
Turbid  urine,  119 
Turpentine,  62 


U 


Urine,  IIS 

ammonia  in,  112 
amount,  115 
casts  in,  129 
collection  of,  120 
deposit  in,  119 
dextrose  in,  126 
glucose  in,  126 
in  jaundice,  118 
measuring,  116 
pus  in,  121 
preservative  for,  120 
reaction,  122 
retention,  117 
specific  gravity  of,  122 
suppression,  117 
turbid,  119 


Valence,  183,  24 
Venous  blood,  35 
Vinegar,  63,  73 

W 

Water,  3 

composition  of,  26 

hard,  88 
Whey,  93,  106 
Wood  fiber,  78 


Urates,  119 
Urea,  57,  114 
Uric  acid,  114 


Yeast,  71,  72 


Zinc,  11 

Zinc  chloride,  39 

Zinc  sulphate,  11 

Zinc  svilphocarbolate,  11 


Printed  in  the  United  States  of  America. 


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1921  J 


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